Using indexers from multiple systems

ABSTRACT

In embodiments, at a first cluster, information identifying a plurality of indexers of the first cluster is determined based on a master node of the first cluster identifying active indexers within the first cluster. The information is transmitted from the first cluster to a second cluster. Such information can include a list of active indexers, and an indication of how to communicate with the plurality of indexers that is used by the second cluster in distributing a distributed search query. The distributed search query is received at the plurality of indexers of the first cluster. The distributed search query is distributed across the plurality of indexers based on the information identifying the plurality of indexers. A response is provided from at least one of the plurality of indexers, wherein each response from a respective indexer is generated based on an evaluation of the distributed search query.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/967,478, filed Apr. 30, 2018, entitled “Multi-Site Cluster-Based DataIntake And Query Systems,” which is itself a continuation of U.S. patentapplication Ser. No. 14/526,493, filed Oct. 28, 2014, entitled “HybridCluster-Based Data Intake And Query,” which claims the benefit of U.S.Provisional Application No. 62/057,973, filed Sep. 30, 2014, entitled“Hybrid Cluster-Based Data Intake And Query.” The entire contents ofeach of the foregoing applications are incorporated by reference herein.

BACKGROUND

Businesses and their data analysts face the challenge of making sense ofand finding patterns in the increasingly large amounts of data in themany types and formats that such businesses generate and collect. Forexample, accessing computer networks and transmitting electroniccommunications across the networks generates massive amounts of data,including such types of data as machine data and Web logs. Identifyingpatterns in this data, once thought relatively useless, has proven to beof great value to the businesses. In some instances, pattern analysiscan indicate which patterns are normal and which ones are unusual. Forexample, detecting unusual patterns can allow a computer system managerto investigate the circumstances and determine whether a computer systemsecurity threat exists.

Additionally, analysis of the data allows businesses to understand howtheir employees, potential consumers, and/or Web visitors use thecompany's online resources. Such analysis can provide businesses withoperational intelligence, business intelligence, and an ability tobetter manage their IT resources. For instance, such analysis may enablea business to better retain customers, meet customer needs, or improvethe efficiency of the company's IT resources. Despite the value that onecan derive from the underlying data described, making sense of this datato realize that value takes effort. In particular, patterns inunderlying data may be difficult to identify or understand whenanalyzing specific behaviors in isolation, often resulting in thefailure of a data analyst to notice valuable correlations in the datafrom which a business can draw strategic insight.

BRIEF SUMMARY OF THE INVENTION

This Summary introduces a selection of concepts in a simplified formthat are further described below in the Detailed Description. As such,this Summary is not intended to identify essential features of theclaimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

The various embodiments describe multi-site cluster-based data intakeand query systems, including cloud-based data intake and query systems.Using a hybrid search system that includes cloud-based data intake andquery systems working in concert with so-called “on-premises” dataintake and query systems can promote the scalability of searchfunctionality. In addition, the hybrid search system can enable dataisolation in a manner in which sensitive data is maintained “onpremises” and information or data that is not sensitive can be moved tothe cloud-based system. Further, the cloud-based system can enableefficient leveraging of data that may already exist in the cloud.

In addition, various embodiments enable configuration data associatedwith search functionality to be shared amongst clusters in a manner thatpromotes cluster security. Specifically, a shared data store can beutilized to store configuration information such that when a particularcluster wishes to use the configuration information, it simply retrievesthe configuration information from the shared data store, thus avoidingdirect communication with other clusters.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different instances in thedescription and the figures may indicate similar or identical items.Entities represented in the figures may be indicative of one or moreentities and thus reference may be made interchangeably to single orplural forms of the entities in the discussion.

FIG. 1 presents a block diagram of an event-processing system inaccordance with the disclosed implementations.

FIG. 2 presents a flowchart illustrating how indexers process, index,and store data received from forwarders in accordance with the disclosedimplementations.

FIG. 3 presents a flowchart illustrating how a search head and indexersperform a search query in accordance with the disclosed implementations.

FIG. 4 presents a block diagram of a system for processing searchrequests that uses extraction rules for field values in accordance withthe disclosed implementations.

FIG. 5 illustrates an exemplary search query received from a client andexecuted by search peers in accordance with the disclosedimplementations.

FIG. 6A illustrates a search screen in accordance with the disclosedimplementations.

FIG. 6B illustrates a data summary dialog that enables a user to selectvarious data sources in accordance with the disclosed implementations.

FIG. 7A illustrates a key indicators view in accordance with thedisclosed implementations.

FIG. 7B illustrates an incident review dashboard in accordance with thedisclosed implementations.

FIG. 7C illustrates a proactive monitoring tree m accordance with thedisclosed implementations.

FIG. 7D illustrates a screen displaying both log data and performancedata in accordance with the disclosed implementations.

FIG. 8 presents a block diagram of an event-processing system inaccordance with the disclosed implementations.

FIG. 9 presents a flowchart illustrating how data can be replicated inaccordance with the disclosed implementations.

FIG. 10 presents a block diagram of a multi-cluster event-processingsystem in accordance with the disclosed implementations.

FIG. 11 presents a flowchart illustrating how data can be replicated inaccordance with the disclosed implementations.

FIG. 11A presents a flowchart illustrating how a search can be performedin accordance with the disclosed implementations.

FIG. 12A presents a block diagram of a multi-cluster event-processingsystem in accordance with the disclosed implementations.

FIG. 12B presents a flowchart illustrating how a search can be performedin accordance with the disclosed implementations.

FIG. 13 presents a flowchart illustrating how a search can be performedin accordance with the disclosed implementations.

FIG. 14 presents a block diagram of an event-processing system,including a cloud-based cluster, in accordance with the disclosedimplementations.

FIG. 15 presents a flowchart illustrating how a search can be performedin accordance with the disclosed implementations.

FIG. 16 presents a block diagram of an event-processing system,including a cloud-based cluster, in accordance with the disclosedimplementations.

FIG. 17 presents a flowchart illustrating how a search can be performedin accordance with the disclosed implementations.

FIG. 18 presents a block diagram of an event-processing system,including a cloud-based cluster in which configuration information canbe shared, in accordance with the disclosed implementations.

FIG. 19 presents a flowchart illustrating how configuration informationcan be shared and used in accordance with the disclosed implementations.

FIG. 20 illustrates an example system including various components of anexample device that can be implemented as any type of computing deviceto implement embodiments of the techniques described herein.

DETAILED DESCRIPTION

Overview

The various embodiments describe multi-site cluster-based data intakeand query systems, including cloud-based data intake and query systems.Using a hybrid search system that includes cloud-based data intake andquery systems working in concert with so-called “on-premises” dataintake and query systems can promote the scalability of searchfunctionality. In addition, the hybrid search system can enable dataisolation in a manner in which sensitive data is maintained “onpremises” and information or data that is not sensitive can be moved tothe cloud-based system. Further, the cloud-based system can enableefficient leveraging of data that may already exist in the cloud.

In addition, various embodiments enable configuration data associatedwith search functionality to be shared amongst clusters in a manner thatpromotes cluster security. Specifically, a shared data store can beutilized to store configuration information such that when a particularcluster wishes to use the configuration information, it simply retrievesthe configuration information from the shared data store, thus avoidingdirect communication with other clusters.

In the following discussion, an example environment is first describedthat may employ the techniques described herein. Example procedures arethen described which may be performed in the example environment as wellas other environments. Consequently, performance of the exampleprocedures is not limited to the example environment and the exampleenvironment is not limited to performance of the example procedures.

Example Environment

Modern data centers often comprise thousands of host computer systemsthat operate collectively to service requests from even larger numbersof remote clients. During operation, these data centers generatesignificant volumes of performance data and diagnostic information thatcan be analyzed to quickly diagnose performance problems. In order toreduce the size of this performance data, the data is typicallypre-processed prior to being stored based on anticipated data-analysisneeds. For example, pre-specified data items can be extracted from theperformance data and stored in a database to facilitate efficientretrieval and analysis at search time. However, the rest of theperformance data is not saved and is essentially discarded duringpre-processing. As storage capacity becomes progressively cheaper andmore plentiful, there are fewer incentives to discard this performancedata and many reasons to keep it.

This plentiful storage capacity is presently making it feasible to storemassive quantities of minimally processed performance data at “ingestiontime” for later retrieval and analysis at “search time.” Note thatperforming the analysis operations at search time provides greaterflexibility because it enables an analyst to search all of theperformance data, instead of searching pre-specified data items thatwere stored at ingestion time. This enables the analyst to investigatedifferent aspects of the performance data instead of being confined tothe pre-specified set of data items that were selected at ingestiontime.

However, analyzing massive quantities of heterogeneous performance dataat search time can be a challenging task. A data center may generateheterogeneous performance data from thousands of different components,which can collectively generate tremendous volumes of performance datathat can be time-consuming to analyze. For example, this performancedata can include data from system logs, network packet data, sensordata, and data generated by various applications. Also, the unstructurednature of much of this performance data can pose additional challengesbecause of the difficulty of applying semantic meaning to unstructureddata, and the difficulty of indexing and querying unstructured datausing traditional database systems.

These challenges can be addressed by using an event-based system, suchas the SPLUNK® ENTERPRISE system produced by Splunk Inc. of SanFrancisco, Calif., to store and process performance data. The SPLUNK®ENTERPRISE system is the leading platform for providing real-timeoperational intelligence that enables organizations to collect, index,and harness machine-generated data from various websites, applications,servers, networks, and mobile devices that power their businesses. TheSPLUNK® ENTERPRISE system is particularly useful for analyzingunstructured performance data, which is commonly found in system logfiles. Although many of the techniques described herein are explainedwith reference to the SPLUNK® ENTERPRISE system, the techniques are alsoapplicable to other types of data server systems.

In the SPLUNK® ENTERPRISE system, performance data is stored as“events,” in which each event comprises a collection of performance dataand/or diagnostic information that is generated by a computer system andis correlated with a specific point in time. Events can be derived from“time series data,” in which time series data includes a sequence ofdata points (e.g., performance measurements from a computer system) thatare associated with successive points in time and are typically spacedat uniform time intervals. Events can also be derived from “structured”or “unstructured” data. Structured data has a predefined format, inwhich specific data items with specific data formats reside atpredefined locations in the data. For example, structured data caninclude data items stored in fields in a database table. In contrast,unstructured data does not have a predefined format. This means thatunstructured data can include various data items having different datatypes that can reside at different locations. For example, when the datasource is an operating system log, an event can include one or morelines from the operating system log containing raw data that includesdifferent types of performance and diagnostic information associatedwith a specific point in time. Examples of data sources from which anevent may be derived include, but are not limited to: web servers;application servers; databases; firewalls; routers; operating systems;and software applications that execute on computer systems, mobiledevices, and sensors. The data generated by such data sources can beproduced in various forms including, for example and without limitation,server log files, activity log files, configuration files, messages,network packet data, performance measurements and sensor measurements.An event typically includes a timestamp that may be derived from the rawdata in the event, or may be determined through interpolation betweentemporally proximate events having known timestamps.

The SPLUNK® ENTERPRISE system also facilitates using a flexible schemato specify how to extract information from the event data, in which theflexible schema may be developed and redefined as needed. Note that aflexible schema may be applied to event data “on the fly” as desired(e.g., at search time), rather than at ingestion time of the data as intraditional database systems. Because the schema is not applied to eventdata until it is desired (e.g., at search time), it is referred to as a“late-binding schema.”

During operation, the SPLUNK® ENTERPRISE system starts with raw data,which can include unstructured data, machine data, performancemeasurements or other time-series data, such as data obtained fromweblogs, syslogs, or sensor readings. It divides this raw data into“portions,” and optionally transforms the data to produce timestampedevents. The system stores the timestamped events in a data store, andenables a user to run queries against the data store to retrieve eventsthat meet specified criteria, such as containing certain keywords orhaving specific values in defined fields. Note that the term “field”refers to a location in the event data containing a value for a specificdata item.

As noted above, the SPLUNK® ENTERPRISE system facilitates using alate-binding schema while performing queries on events. A late-bindingschema specifies “extraction rules” that are applied to data in theevents to extract values for specific fields. More specifically, theextraction rules for a field can include one or more instructions thatspecify how to extract a value for the field from the event data. Anextraction rule can generally include any type of instruction forextracting values from data in events. In some cases, an extraction ruleincludes a regular expression, in which case the rule is referred to asa “regex rule.”

In contrast to a conventional schema for a database system, alate-binding schema is not defined at data ingestion time. Instead, thelate-binding schema can be developed on an ongoing basis until the timea query is actually executed. This means that extraction rules for thefields in a query may be provided in the query itself, or may be locatedduring execution of the query. Hence, as an analyst learns more aboutthe data in the events, the analyst can continue to refine the latebinding schema by adding new fields, deleting fields, or changing thefield extraction rules until the next time the schema is used by aquery. Because the SPLUNK® ENTERPRISE system maintains the underlyingraw data and provides a late-binding schema for searching the raw data,it enables an analyst to investigate questions that arise as the analystlearns more about the events.

In the SPLUNK® ENTERPRISE system, a field extractor may be configured toautomatically generate extraction rules for certain fields in the eventswhen the events are being created, indexed, or stored, or possibly at alater time. Alternatively, a user may manually define extraction rulesfor fields using a variety of techniques.

Also, a number of “default fields” that specify metadata about theevents rather than data in the events themselves can be createdautomatically. For example, such default fields can specify: a timestampfor the event data; a host from which the event data originated; asource of the event data; and a source type for the event data. Thesedefault fields may be determined automatically when the events arecreated, indexed or stored.

In some embodiments, a common field name may be used to reference two ormore fields containing equivalent data items, even though the fields maybe associated with different types of events that possibly havedifferent data formats and different extraction rules. By enabling acommon field name to be used to identify equivalent fields fromdifferent types of events generated by different data sources, thesystem facilitates use of a “common information model” (CIM) across thedifferent data sources.

1.2 Data Server System

FIG. 1 presents a block diagram of an exemplary event-processing system100, similar to the SPLUNK® ENTERPRISE system. System 100 includes oneor more forwarders 101 that collect data obtained from a variety ofdifferent data sources 105, and one or more indexers 102 that store,process, and/or perform operations on this data, in which each indexeroperates on data contained in a specific data store 103. Theseforwarders and indexers can comprise separate computer systems m a datacenter, or may alternatively comprise separate processes executing onvarious computer systems in a data center.

During operation, the forwarders 101 identify which indexers 102 willreceive the collected data and then forward the data to the identifiedindexers. Forwarders 101 can also perform operations to strip outextraneous data and detect timestamps in the data. The forwarders nextdetermine which indexers 102 will receive each data item and thenforward the data items to the determined indexers 102.

Note that distributing data across different indexers facilitatesparallel processing. This parallel processing can take place at dataingestion time, because multiple indexers can process the incoming datain parallel. The parallel processing can also take place at search time,because multiple indexers can search through the data in parallel.

System 100 and the processes described below with respect to FIGS. 1-5are further described in “Exploring Splunk Search Processing Language(SPL) Primer and Cookbook” by David Carasso, CITO Research, 2012, and in“Optimizing Data Analysis With a Semi-Structured Time Series Database”by Ledion Bitincka, Archana Ganapathi, Stephen Sorkin, and Steve Zhang,SLAML, 2010, each of which is hereby incorporated herein by reference inits entirety for all purposes.

1.3 Data Ingestion

FIG. 2 presents a flowchart 200 illustrating how an indexer processes,indexes, and stores data received from forwarders in accordance with thedisclosed embodiments. At block 201, the indexer receives the data fromthe forwarder. Next, at block 202, the indexer apportions the data intoevents. Note that the data can include lines of text that are separatedby carriage returns or line breaks and an event may include one or moreof these lines. During the apportioning process, the indexer can useheuristic rules to automatically determine the boundaries of the events,which for example coincide with line boundaries. These heuristic rulesmay be determined based on the source of the data, in which the indexercan be explicitly informed about the source of the data or can infer thesource of the data by examining the data. These heuristic rules caninclude regular expression-based rules or delimiter-based rules fordetermining event boundaries, in which the event boundaries may beindicated by predefined characters or character strings. Thesepredefined characters may include punctuation marks or other specialcharacters including, for example, carriage returns, tabs, spaces orline breaks. In some cases, a user can fine-tune or configure the rulesthat the indexers use to determine event boundaries in order to adaptthe rules to the user's specific requirements.

Next, the indexer determines a timestamp for each event at block 203. Asmentioned above, these timestamps can be determined by extracting thetime directly from data in the event, or by interpolating the time basedon timestamps from temporally proximate events. In some cases, atimestamp can be determined based on the time the data was received orgenerated. The indexer subsequently associates the determined timestampwith each event at block 204, for example by storing the timestamp asmetadata for each event.

Then, the system can apply transformations to data to be included inevents at block 205. For log data, such transformations can includeremoving a portion of an event (e.g., a portion used to define eventboundaries, extraneous text, characters, etc.) or removing redundantportions of an event. Note that a user can specify portions to beremoved using a regular expression or any other possible technique.

Next, a keyword index can optionally be generated to facilitate fastkeyword searching for events. To build a keyword index, the indexerfirst identifies a set of keywords in block 206. Then, at block 207 theindexer includes the identified keywords in an index, which associateseach stored keyword with references to events containing that keyword(or to locations within events where that keyword is located). When anindexer subsequently receives a keyword based query, the indexer canaccess the keyword index to quickly identify events containing thekeyword.

In some embodiments, the keyword index may include entries for namevalue pairs found in events, wherein a name-value pair can include apair of keywords connected by a symbol, such as an equals sign or colon.In this way, events containing these name-value pairs can be quicklylocated. In some embodiments, fields can automatically be generated forsome or all of the name value pairs at the time of indexing. Forexample, if the string “dest=10.0.1.2” is found in an event, a fieldnamed “dest” may be created for the event, and assigned a value of“10.0.1.2.”

Finally, the indexer stores the events in a data store at block 208,wherein a timestamp can be stored with each event to facilitatesearching for events based on a time range. In some cases, the storedevents are organized into a plurality of buckets, wherein each bucketstores events associated with a specific time range. This not onlyimproves time-based searches, but it also allows events with recenttimestamps that may have a higher likelihood of being accessed to bestored in faster memory to facilitate faster retrieval. For example, abucket containing the most recent events can be stored as flash memoryinstead of on hard disk.

Each indexer 102 is responsible for storing and searching a subset ofthe events contained in a corresponding data store 103. By distributingevents among the indexers and data stores, the indexers can analyzeevents for a query in parallel, for example using map-reduce techniques,in which each indexer returns partial responses for a subset of eventsto a search head that combines the results to produce an answer for thequery. By storing events in buckets for specific time ranges, an indexermay further optimize searching by looking only in buckets for timeranges that are relevant to a query.

Moreover, events and buckets can also be replicated across differentindexers and data stores to facilitate high availability and disasterrecovery as is described in U.S. patent application Ser. No. 14/266,812filed on 30 Apr. 2014, and in U.S. patent application Ser. No.14/266,817 also filed on 30 Apr. 2014.

1.4 Query Processing

FIG. 3 presents a flowchart 300 illustrating how a search head andindexers perform a search query in accordance with the disclosedembodiments. At the start of this process, a search head receives asearch query from a client at block 301. Next, at block 302, the searchhead analyzes the search query to determine what portions can bedelegated to indexers and what portions need to be executed locally bythe search head. At block 303, the search head distributes thedetermined portions of the query to the indexers. Note that commandsthat operate on single events can be trivially delegated to theindexers, while commands that involve events from multiple indexers areharder to delegate.

Then, at block 304, the indexers to which the query was distributedsearch their data stores for events that are responsive to the query. Todetermine which events are responsive to the query, the indexer searchesfor events that match the criteria specified in the query. This criteriacan include matching keywords or specific values for certain fields. Ina query that uses a late-binding schema, the searching operations inblock 304 may involve using the late-binding scheme to extract valuesfor specified fields from events at the time the query is processed.Next, the indexers can either send the relevant events back to thesearch head, or use the events to calculate a partial result, and sendthe partial result back to the search head.

Finally, at block 305, the search head combines the partial resultsand/or events received from the indexers to produce a final result forthe query. This final result can comprise different types of datadepending upon what the query is asking for. For example, the finalresults can include a listing of matching events returned by the query,or some type of visualization of data from the returned events. Inanother example, the final result can include one or more calculatedvalues derived from the matching events.

Moreover, the results generated by system 100 can be returned to aclient using different techniques. For example, one technique streamsresults back to a client in real-time as they are identified. Anothertechnique waits to report results to the client until a complete set ofresults is ready to return to the client. Yet another technique streamsinterim results back to the client in real-time until a complete set ofresults is ready, and then returns the complete set of results to theclient. In another technique, certain results are stored as “searchjobs,” and the client may subsequently retrieve the results byreferencing the search jobs.

The search head can also perform various operations to make the searchmore efficient. For example, before the search head starts executing aquery, the search head can determine a time range for the query and aset of common keywords that all matching events must include. Next, thesearch head can use these parameters to query the indexers to obtain asuperset of the eventual results. Then, during a filtering stage, thesearch head can perform field-extraction operations on the superset toproduce a reduced set of search results.

1.5 Field Extraction

FIG. 4 presents a block diagram 400 illustrating how fields can beextracted during query processing in accordance with the disclosedembodiments. At the start of this process, a search query 402 isreceived at a query processor 404. Query processor 404 includes variousmechanisms for processing a query, wherein these mechanisms can residein a search head 104 and/or an indexer 102. Note that the exemplarysearch query 402 illustrated in FIG. 4 is expressed in Search ProcessingLanguage (SPL), which is used in conjunction with the SPLUNK® ENTERPRISEsystem. SPL is a pipelined search language in which a set of inputs isoperated on by a first command in a command line, and then a subsequentcommand following the pipe symbol “I” operates on the results producedby the first command, and so on for additional commands. Search query402 can also be expressed in other query languages, such as theStructured Query Language (“SQL”) or any suitable query language.

Upon receiving search query 402, query processor 404 sees that searchquery 402 includes two fields “IP” and “target.” Query processor 404also determines that the values for the “IP” and “target” fields havenot already been extracted from events in data store 414, andconsequently determines that query processor 404 needs to use extractionrules to extract values for the fields. Hence, query processor 404performs a lookup for the extraction rules in a rule base 406, in whichrule base 406 maps field names to corresponding extraction rules andobtains extraction rules 408-409, extraction rule 408 specifies how toextract a value for the “IP” field from an event, and extraction rule409 specifies how to extract a value for the “target” field from anevent. As is illustrated in FIG. 4 , extraction rules 408-409 caninclude regular expressions that specify how to extract values for therelevant fields. Such regular-expression-based extraction rules are alsoreferred to as “regex rules.” In addition to specifying how to extractfield values, the extraction rules may also include instructions forderiving a field value by performing a function on a character string orvalue retrieved by the extraction rule. For example, a transformationrule may truncate a character string, or convert the character stringinto a different data format. In some cases, the query itself canspecify one or more extraction rules.

Next, query processor 404 sends extraction rules 408-409 to a fieldextractor 412, which applies extraction rules 408-409 to events 416-418in a data store 414. Note that data store 414 can include one or moredata stores, and extraction rules 408-409 can be applied to largenumbers of events in data store 414, and are not meant to be limited tothe three events 416-418 illustrated in FIG. 4 . Moreover, the queryprocessor 404 can instruct field extractor 412 to apply the extractionrules to all the events in a data store 414, or to a subset of theevents that have been filtered based on some criteria.

Next, field extractor 412 applies extraction rule 408 for the firstcommand “Search IP=“10*” to events in data store 414 including events416-418. Extraction rule 408 is used to extract values for the IPaddress field from events in data store 414 by looking for a pattern ofone or more digits, followed by a period, followed again by one or moredigits, followed by another period, followed again by one or moredigits, followed by another period, and followed again by one or moredigits. Next, field extractor 412 returns field values 420 to queryprocessor 404, which uses the criterion IP=“10*” to look for IPaddresses that start with “10”. Note that events 416 and 417 match thiscriterion, but event 418 does not, so the result set for the firstcommand is events 416-417.

Query processor 404 then sends events 416-41 7 to the next command“stats count target.” To process this command, query processor 404causes field extractor 412 to apply extraction rule 409 to events416-417. Extraction rule 409 is used to extract values for the targetfield for events 416-417 by skipping the first four commas in events416-417, and then extracting all of the following characters until acomma or period is reached. Next, field extractor 412 returns fieldvalues 421 to query processor 404, which executes the command “statscount target” to count the number of unique values contained in thetarget fields, which in this example produces the value “2” that isreturned as a final result 422 for the query.

Note that query results can be returned to a client, a search head, orany other system component for further processing. In general, queryresults may include: a set of one or more events; a set of one or morevalues obtained from the events; a subset of the values; statisticscalculated based on the values; a report containing the values; or avisualization, such as a graph or chart, generated from the values.

1.6 Exemplary Search Screen

FIG. 6A illustrates an exemplary search screen 600 in accordance withthe disclosed embodiments. Search screen 600 includes a search bar 602that accepts user input in the form of a search string. It also includesa time range picker 612 that enables the user to specify a time rangefor the search. For “historical searches” the user can select a specifictime range, or alternatively a relative time range, such as “today,”“yesterday” or “last week.” For “real-time searches,” the user canselect the size of a preceding time window to search for real-timeevents. Search screen 600 also initially displays a “data summary”dialog as is illustrated in FIG. 6B that enables the user to selectdifferent sources for the event data, for example by selecting specifichosts and log files.

After the search is executed, the search screen 600 can display theresults through search results tabs 604, wherein search results tabs 604includes: an “events tab” that displays various information about eventsreturned by the search; a “statistics tab” that displays statisticsabout the search results; and a “visualization tab” that displaysvarious visualizations of the search results. The events tab illustratedin FIG. 6A displays a timeline graph 605 that graphically illustratesthe number of events that occurred in one-hour intervals over theselected time range. It also displays an events list 608 that enables auser to view the raw data in each of the returned events. Itadditionally displays a fields sidebar 606 that includes statisticsabout occurrences of specific fields in the returned events, including“selected fields” that are pre-selected by the user, and “interestingfields” that are automatically selected by the system based onprespecified criteria.

1.7 Acceleration Techniques

The above-described system provides significant flexibility by enablinga user to analyze massive quantities of minimally processed performancedata “on the fly” at search time instead of storing pre-specifiedportions of the performance data in a database at ingestion time. Thisflexibility enables a user to see correlations in the performance dataand perform subsequent queries to examine interesting aspects of theperformance data that may not have been apparent at ingestion time.

However, performing extraction and analysis operations at search timecan involve a large amount of data and require a large number ofcomputational operations, which can cause considerable delays whileprocessing the queries. Fortunately, a number of acceleration techniqueshave been developed to speed up analysis operations performed at searchtime. These techniques include: (1) performing search operations inparallel by formulating a search as a map-reduce computation; (2) usinga keyword index; (3) using a high performance analytics store; and (4)accelerating the process of generating reports. These techniques aredescribed in more detail below.

1.7.1 Map-Reduce Technique

To facilitate faster query processing, a query can be structured as amap-reduce computation, wherein the “map” operations are delegated tothe indexers, while the corresponding “reduce” operations are performedlocally at the search head. For example, FIG. 5 illustrates an example500 of how a search query 501 received from a client at search head 104can split into two phases, including: (1) a “map phase” comprisingsubtasks 502 (e.g., data retrieval or simple filtering) that may beperformed in parallel and are “mapped” to indexers 1 02 for execution,and (2) a “reduce phase” comprising a merging operation 503 to beexecuted by the search head when the results are ultimately collectedfrom the indexers.

During operation, upon receiving search query 501, search head 104modifies search query 501 by substituting “stats” with “prestats” toproduce search query 502, and then distributes search query 502 to oneor more distributed indexers, which are also referred to as “searchpeers.” Note that search queries may generally specify search criteriaor operations to be performed on events that meet the search criteria.Search queries may also specify field names, as well as search criteriafor the values in the fields or operations to be performed on the valuesin the fields. Moreover, the search head may distribute the full searchquery to the search peers as is illustrated in FIG. 3 , or mayalternatively distribute a modified version (e.g., a more restrictedversion) of the search query to the search peers. In this example, theindexers are responsible for producing the results and sending them tothe search head. After the indexers return the results to the searchhead, the search head performs the merging operations 503 on theresults. Note that by executing the computation in this way, the systemeffectively distributes the computational operations while minimizingdata transfers.

1.7.2 Keyword Index

As described above with reference to the flow charts 200, 300 in FIGS. 2and 3 , event-processing system 100 can construct and maintain one ormore keyword indices to facilitate rapidly identifying events containingspecific keywords. This can greatly speed up the processing of queriesinvolving specific keywords. As mentioned above, to build a keywordindex, an indexer first identifies a set of keywords. Then, the indexerincludes the identified keywords in an index, which associates eachstored keyword with references to events containing that keyword, or tolocations within events where that keyword is located. When an indexersubsequently receives a keyword-based query, the indexer can access thekeyword index to quickly identify events containing the keyword.

1.7.3 High Performance Analytics Store

To speed up certain types of queries, some embodiments of system 100make use of a high performance analytics store, which is referred to asa “summarization table,” that contains entries for specific field-valuepairs. Each of these entries keeps track of instances of a specificvalue in a specific field in the event data and includes references toevents containing the specific value in the specific field. For example,an exemplary entry in a summarization table can keep track ofoccurrences of the value “94107” in a “ZIP code” field of a set ofevents, wherein the entry includes references to all of the events thatcontain the value “94107” in the ZIP code field. This enables the systemto quickly process queries that seek to determine how many events have aparticular value for a particular field, because the system can examinethe entry in the summarization table to count instances of the specificvalue in the field without having to go through the individual events ordo extractions at search time. Also, if the system needs to process eachof the events that have a specific field-value combination, the systemcan use the references in the summarization table entry to directlyaccess the events to extract further information without having tosearch each of the events to find the specific field-value combinationat search time.

In some embodiments, the system maintains a separate summarization tablefor each of the above-described time-specific buckets that stores eventsfor a specific time range, wherein a bucket-specific summarization tableincludes entries for specific field-value combinations that occur inevents in the specific bucket. Alternatively, the system can maintain aseparate summarization table for each indexer, in which theindexer-specific summarization table only includes entries for theevents in a data store that is managed by the specific indexer.

The summarization table can be populated by running a “collection query”that scans a set of events to find instances of a specific field-valuecombination, or alternatively instances of all field-value combinationsfor a specific field. A collection query can be initiated by a user, orcan be scheduled to occur automatically at specific time intervals. Acollection query can also be automatically launched in response to aquery that asks for a specific field-value combination.

In some cases, the summarization tables may not cover each of the eventsthat are relevant to a query. In this case, the system can use thesummarization tables to obtain partial results for the events that arecovered by summarization tables, but may also have to search throughother events that are not covered by the summarization tables to produceadditional results. These additional results can then be combined withthe partial results to produce a final set of results for the query.This summarization table and associated techniques are described in moredetail in U.S. Pat. No. 8,682,925, issued on Mar. 25, 2014.

1.7.4 Accelerating Report Generation

In some embodiments, a data server system such as the SPLUNK® ENTERPRISEsystem can accelerate the process of periodically generating updatedreports based on query results. To accelerate this process, asummarization engine automatically examines the query to determinewhether generation of updated reports can be accelerated by creatingintermediate summanes. (This is possible if results from preceding timeperiods can be computed separately and combined to generate an updatedreport. In some cases, it is not possible to combine such incrementalresults, for example where a value in the report depends onrelationships between events from different time periods.) If reportscan be accelerated, the summarization engine periodically generates asummary covering data obtained during a latest non-overlapping timeperiod. For example, where the query seeks events meeting a specifiedcriteria, a summary for the time period includes only events within thetime period that meet the specified criteria. Similarly, if the queryseeks statistics calculated from the events, such as the number ofevents that match the specified criteria, then the summary for the timeperiod includes the number of events in the period that match thespecified criteria.

In parallel with the creation of the summaries, the summarization engineschedules the periodic updating of the report associated with the query.During each scheduled report update, the query engine determines whetherintermediate summaries have been generated covering portions of the timeperiod covered by the report update. If so, then the report is generatedbased on the information contained in the summaries. Also, if additionalevent data has been received and has not yet been summarized, and isrequired to generate the complete report, the query can be run on thisadditional event data. Then, the results returned by this query on theadditional event data, along with the partial results obtained from theintermediate summaries, can be combined to generate the updated report.This process is repeated each time the report is updated. Alternatively,if the system stores events in buckets covering specific time ranges,then the summaries can be generated on a bucket-by-bucket basis. Notethat producing intermediate summaries can save the work involved inre-running the query for previous time periods, so only the newer eventdata needs to be processed while generating an updated report. Thesereport acceleration techniques are described in more detail in U.S. Pat.No. 8,589,403, issued on Nov. 19, 2013, and U.S. Pat. No. 8,412,696,issued on Apr. 2, 2011.

1.8 Security Features

The SPLUNK® ENTERPRISE platform provides various schemas, dashboards andvisualizations that make it easy for developers to create applicationsto provide additional capabilities. One such application is the SPLUNK®APP FOR ENTERPRISE SECURITY, which performs monitoring and alertingoperations and includes analytics to facilitate identifying both knownand unknown security threats based on large volumes of data stored bythe SPLUNK® ENTERPRISE system. This differs significantly fromconventional Security Information and Event Management (SIEM) systemsthat lack the infrastructure to effectively store and analyze largevolumes of security-related event data. Traditional SIEM systemstypically use fixed schemas to extract data from pre-definedsecurity-related fields at data ingestion time, wherein the extracteddata is typically stored in a relational database. This data extractionprocess (and associated reduction in data size) that occurs at dataingestion time inevitably hampers future incident investigations, whenall of the original data may be needed to determine the root cause of asecurity issue, or to detect the tiny fingerprints of an impendingsecurity threat.

In contrast, the SPLUNK® APP FOR ENTERPRISE SECURITY system stores largevolumes of minimally processed security-related data at ingestion timefor later retrieval and analysis at search time when a live securitythreat is being investigated. To facilitate this data retrieval process,the SPLUNK® APP FOR ENTERPRISE SECURITY provides pre-specified schemasfor extracting relevant values from the different types ofsecurity-related event data, and also enables a user to define suchschemas.

The SPLUNK® APP FOR ENTERPRISE SECURITY can process many types ofsecurity-related information. In general, this security-relatedinformation can include any information that can be used to identifysecurity threats. For example, the security-related information caninclude network-related information, such as IP addresses, domain names,asset identifiers, network traffic volume, uniform resource locatorstrings, and source addresses. (The process of detecting securitythreats for network-related information is further described in U.S.patent application Ser. Nos. 13/956,252, and 13/956,262.)Security-related information can also include endpoint information, suchas malware infection data and system configuration information, as wellas access control information, such as login/logout information andaccess failure notifications. The security-related information canoriginate from various sources within a data center, such as hosts,virtual machines, storage devices and sensors. The security-relatedinformation can also originate from various sources in a network, suchas routers, switches, email servers, proxy servers, gateways, firewallsand intrusion-detection systems.

During operation, the SPLUNK® APP FOR ENTERPRISE SECURITY facilitatesdetecting so-called “notable events” that are likely to indicate asecurity threat. These notable events can be detected in a number ofways: (1) an analyst can notice a correlation in the data and canmanually identify a corresponding group of one or more events as“notable;” or (2) an analyst can define a “correlation search”specifying criteria for a notable event, and every time one or moreevents satisfy the criteria, the application can indicate that the oneor more events are notable. An analyst can alternatively select apre-defined correlation search provided by the application. Note thatcorrelation searches can be run continuously or at regular intervals(e.g., every hour) to search for notable events. Upon detection, notableevents can be stored in a dedicated “notable events index,” which can besubsequently accessed to generate various visualizations containingsecurity-related information. Also, alerts can be generated to notifysystem operators when important notable events are discovered.

The SPLUNK® APP FOR ENTERPRISE SECURITY provides various visualizationsto aid in discovering security threats, such as a “key indicators view”that enables a user to view security metrics of interest, such as countsof different types of notable events. For example, FIG. 7A illustratesan exemplary key indicators view 700 that comprises a dashboard, whichcan display a value 701, for various security-related metrics, such asmalware infections 702. It can also display a change in a metric value703, which indicates that the number of malware infections increased by63 during the preceding interval. Key indicators view 700 additionallydisplays a histogram panel 704 that displays a histogram of notableevents organized by urgency values, and a histogram of notable eventsorganized by time intervals. This key indicators view is described infurther detail in pending U.S. patent application Ser. No. 13/956,338filed Jul. 31, 2013.

These visualizations can also include an “incident review dashboard”that enables a user to view and act on “notable events.” These notableevents can include: (1) a single event of high importance, such as anyactivity from a known web attacker; or (2) multiple events thatcollectively warrant review, such as a large number of authenticationfailures on a host followed by a successful authentication. For example,FIG. 7B illustrates an exemplary incident review dashboard 710 thatincludes a set of incident attribute fields 711 that, for example,enables a user to specify a time range field 712 for the displayedevents. It also includes a timeline 713 that graphically illustrates thenumber of incidents that occurred in one-hour time intervals over theselected time range. It additionally displays an events list 714 thatenables a user to view a list of each of the notable events that matchthe criteria in the incident attributes fields 711. To facilitateidentifying patterns among the notable events, each notable event can beassociated with an urgency value (e.g., low, medium, high, critical),which is indicated in the incident review dashboard. The urgency valuefor a detected event can be determined based on the severity of theevent and the priority of the system component associated with theevent. The incident review dashboard is described further in“http://docs.splunk.com/Documentation/PCI/2.1.1/User/IncidentReviewdashboard”

1.9 Data Center Monitoring

As mentioned above, the SPLUNK® ENTERPRISE platform provides variousfeatures that make it easy for developers to create variousapplications. One such application is the SPLUNK® APP FOR VMWARE®, whichperforms monitoring operations and includes analytics to facilitatediagnosing the root cause of performance problems in a data center basedon large volumes of data stored by the SPLUNK® ENTERPRISE system.

This differs from conventional data-center-monitoring systems that lackthe infrastructure to effectively store and analyze large volumes ofperformance information and log data obtained from the data center. Inconventional datacenter-monitoring systems, this performance data istypically pre-processed prior to being stored, for example by extractingpre-specified data items from the performance data and storing them in adatabase to facilitate subsequent retrieval and analysis at search time.However, the rest of the performance data is not saved and isessentially discarded during pre-processing. In contrast, the SPLUNK®APP FOR VMWARE® stores large volumes of minimally processed performanceinformation and log data at ingestion time for later retrieval andanalysis at search time when a live performance issue is beinginvestigated.

The SPLUNK® APP FOR VMW ARE® can process many types ofperformance-related information. In general, this performance-relatedinformation can include any type of performance-related data and logdata produced by virtual machines and host computer systems in a datacenter. In addition to data obtained from various log files, thisperformance-related information can include values for performancemetrics obtained through an application programming interface (API)provided as part of the vSphere Hypervisor™ system distributed byVMware, Inc. of Palo Alto, Calif. For example, these performance metricscan include: (1) CPU-related performance metrics; (2) disk-relatedperformance metrics; (3) memory-related performance metrics; (4)network-related performance metrics; (5) energy-usage statistics; (6)data-traffic-related performance metrics; (7) overall systemavailability performance metrics; (8) cluster-related performancemetrics; and (9) virtual machine performance statistics. For moredetails about such performance metrics, please see U.S. patent Ser. No.14/167,316 filed 29 Jan. 2014, which is hereby incorporated herein byreference. Also, see “vSphere Monitoring and Performance,” Update 1,vSphere 5.5, EN-001357-00,http://pubs.vmware.com/vsphere-55/topic/com.vmware.ICbase/PDF/vsphereesxi-vcenter-server-551-monitoring-performance-guide.pdf.

To facilitate retrieving information of interest from performance dataand log files, the SPLUNK® APP FOR VMW ARE® provides pre-specifiedschemas for extracting relevant values from different types ofperformance-related event data, and also enables a user to define suchschemas.

The SPLUNK® APP FOR VMW ARE® additionally provides variousvisualizations to facilitate detecting and diagnosing the root cause ofperformance problems. For example, one such visualization is a“proactive monitoring tree” that enables a user to easily view andunderstand relationships among various factors that affect theperformance of a hierarchically structured computing system. Thisproactive monitoring tree enables a user to easily navigate thehierarchy by selectively expanding nodes representing various entities(e.g., virtual centers or computing clusters) to view performanceinformation for lower-level nodes associated with lower-level entities(e.g., virtual machines or host systems). Exemplary node-expansionoperations are illustrated in FIG. 7C, wherein nodes 733 and 734 areselectively expanded. Note that nodes 731-739 can be displayed usingdifferent patterns or colors to represent different performance states,such as a critical state, a warning state, a normal state or anunknown/offline state. The ease of navigation provided by selectiveexpansion in combination with the associated performance-stateinformation enables a user to quickly diagnose the root cause of aperformance problem. The proactive monitoring tree is described infurther detail in U.S. patent application Ser. No. 14/235,490 filed on15 Apr. 2014, which is hereby incorporated herein by reference for allpossible purposes.

The SPLUNK® APP FOR VMW ARE® also provides a user interface that enablesa user to select a specific time range and then view heterogeneous data,comprising events, log data and associated performance metrics, for theselected time range. For example, the screen illustrated in FIG. 7Ddisplays a listing of recent “tasks and events” and a listing of recent“log entries” for a selected time range above a performance-metric graphfor “average CPU core utilization” for the selected time range. Notethat a user is able to operate pull-down menus 742 to selectivelydisplay different performance metric graphs for the selected time range.This enables the user to correlate trends in the performance-metricgraph with corresponding event and log data to quickly determine theroot cause of a performance problem. This user interface is described inmore detail in U.S. patent application Ser. No. 14/167,316 filed on 29Jan. 2014, which is hereby incorporated herein by reference for allpossible purposes.

2.0 Clustered Operating Environment

It should be appreciated that, to achieve high availability and toprovide for disaster recovery of data stored in a system such as thedata intake and query system illustrated in FIG. 1 , the system may beconfigured to operate as a cluster. A clustered data intake and querysystem as described herein generally may include multiple systemcomponents (e.g., forwarders, indexers, data stores, and/or searchheads) configured to operate together in a coordinated fashion. Toprovide for high availability and disaster recovery in a clusteredsystem, data processed and stored by an indexer in a data store may bereplicated across one or more other indexers and data stores of thecluster according to a user configurable data replication policy. In oneembodiment, a specialized cluster component, referred to herein as amaster node, may be configured to coordinate various aspects ofreplicating data across data stores of the cluster and performingsearches against data that has been replicated in a cluster. There aremany options for how data may be replicated in a cluster and, in oneembodiment, the manner in which data is replicated in a particularcluster may be based in part on a user configurable data replicationpolicy. One configurable component of a data replication policy may bereferred to as a “replication factor.” The replication factor for acluster is a value indicating a number of copies of each data subset, orbucket, created by an indexer that are to be stored across otherindexers and in separate data stores of the cluster. For example, acluster configured with a replication factor of two (2) indicates thatfor each data bucket created by an indexer, one additional copy of thebucket is to be created and stored by a different indexer of thecluster. Similarly, a cluster configured with a replication factor offour (4) indicates that each data bucket created by an indexer is to bereplicated by three additional indexers of the cluster. In this manner,a cluster configured with a particular replication factor generally cantolerate a concurrent failure of a number of indexers that is one lessthan the replication factor.

As indicated above, when an indexer receives data from a forwarder, theindexer may store the data in one or more grouped subsets, or buckets,each corresponding to a time range associated with the data in thebucket. Each bucket created by an indexer may contain at least two typesof files: event data extracted from the raw data and, optionally, a keyword index that enables searches to be performed on the event data. Inone embodiment, each replicated copy of a bucket created according to adata replication policy may either be searchable, meaning the bucketincludes a copy of the key word index, or non-searchable, meaning thebucket includes only a copy of the event data and is not immediatelysearchable. To determine a number of searchable copies of each bucket tostore in the cluster, a data replication policy may further beconfigured with a “search factor.” A search factor is similar to areplication factor except that it indicates a number of searchablecopies of each bucket to store in the cluster. For example, a clustermay be configured with a search factor of one (1), indicating that onlyone of the copies of a bucket is to include a key word index. However,if a search factor of greater than one is configured, some or all of theindexers storing a replicated copy of a bucket also may generate indexfiles for the buckets they are replicating, or the indexers may receivea copy of the index files from another indexer.

A cluster may be configured with a different replication factor andsearch factor. For example, a particular cluster may be configured witha replication factor of three (3) and a search factor of two (2). Basedon this example data replication policy, the cluster maintains threecopies of each bucket in the cluster; however, only two of the copies ofeach bucket contain index files and are therefore capable of respondingto search requests. The indexers storing the third copy of each bucketthat does not include the index files may not be able to respond tosearch requests, but the bucket can be made searchable at a later timeby causing the indexer storing the bucket to generate the appropriateindex files or to receive the index files from another indexer. Forexample, a non-searchable copy of a bucket may be made searchable due toone or more indexers storing a searchable copy of the bucketexperiencing a failure.

As indicated above, a cluster configured with a data replication policycauses replicated copies to be stored of each bucket created by anindexer of the cluster. When a search query is received by a search headassociated with the cluster, the search head may distribute the searchquery to all of the indexers of a cluster. However, if multiple indexersin the cluster store copies of one or more buckets that contain datathat partially satisfies the search query, duplicate search results maybe returned to the search head. To ensure that only one indexer of acluster returns results from each bucket when multiple copies of thebuckets exist in the cluster, one indexer is designated as the “primary”indexer for each bucket while other indexers storing copies of the samebucket are designated as “secondary” indexers. An indexer that isdesignated as the primary indexer for a bucket has primaryresponsibility for returning results from that bucket that areresponsive to search queries received by the primary indexer, whilesecondary indexers do not respond to search queries with results fromsecondary copies of the same bucket. In other words, when an indexer ofa cluster receives a search query from a search head, the indexer findsevents in buckets for which the indexer is the primary indexer and thatsatisfy the search query criteria. In an alternative embodiment, theother indexers storing copies of the same bucket are simply notdesignated as the primary indexer for the bucket.

For each bucket that is replicated across multiple indexers of acluster, the designation of one indexer as the primary indexer and otherindexers as secondary indexers may change over time. In one embodiment,a mapping of cluster indexers as either the primary indexer or asecondary indexer for each bucket may be represented using the conceptof a “generation.” In general, a generation represents a “snapshot” ofthe cluster at a particular point in time and identifies which indexersare primary and which indexers are secondary for each bucket andreplicated copy of a bucket stored in the cluster. A centralized “masternode” of the cluster may be responsible for creating a generationmapping and distributing the generation mapping to other components ofthe cluster. A master node may create multiple different generationswith different mappings over time as conditions within the clusterchange. Each generation may be identified by a unique generationidentifier represented, for example, by a monotonically increasingcounter or other set of unique values. For example, a first generationmay be represented by a generation identifier of zero (generation 0), asecond generation represented by a generation identifier of one(generation 1), and so forth. Thus, for a first generation 0, aparticular indexer X of a cluster may be designated as the primaryindexer for a particular bucket Z that is replicated across a number ofindexers in the cluster. At a later time, a new generation 1 may becreated and a different indexer Y instead may be designated as theprimary indexer for the same bucket Z. A master node may create newgenerations and corresponding generation identifiers in response to anumber of different cluster events including, but not limited to, anyof: the master node initializing, a new indexer joining the cluster, acurrent indexer failing or leaving the cluster, to rebalance the bucketsof a cluster, etc.

FIG. 8 shows a block diagram of an example embodiment of a clustereddata intake and query system, according to one embodiment. Similar tothe system 100 of FIG. 1 , cluster 800 includes one or more forwarders801 that collect data from a variety of different data sources 805 andwhich determine which indexer or indexers (e.g., one or more of indexers802A-802C) are to receive the data. An indexer 802A-802C receiving datafrom a forwarder 801 may perform various operations to process, index,and store the data in a corresponding data store 803A-803C. The dataprocessed by an indexer 802A-802C may be stored in a corresponding datastore 803A-803C in one or more grouped subsets, or buckets, thatcorrespond to various time ranges. For example, each of data stores803A-803C is depicted in FIG. 8 as storing one or more example buckets1A, 1B, 2A, 2B, 3A, and 3B. In this example, “A” and “B” versions of abucket represent copies of the same bucket.

In cluster 800, a search head 804 is responsible for distributing searchqueries received from clients to indexers 802A-802C and consolidatingany search results received from the indexers. For example, a searchhead 804 may distribute a search query to indexers 802A-802C whichperform the actual searches against the buckets stored by the indexersin data stores 803A-803C.

To perform a search against data stored by cluster 800, in oneembodiment, a search head 804 may first obtain information from masternode 806 including a list of active indexers and a generationidentifier. As indicated above, a generation identifier identifies aparticular generation mapping which indicates, for each bucket in thecluster, which indexer is the primary indexer and which indexers aresecondary indexers.

The search head 804 may distribute the search query to all of the activeindexers along with the generation identifier. Each indexer receivingthe search query may use the generation identifier to identify whichgeneration mapping to consult when searching the buckets stored by theindexer. In other words, based on the generation informationcorresponding to the received generation identifier, each indexersearches for event results in buckets for which the indexer is theprimary indexer and which satisfy the search query criteria. Afterprocessing the search query, each indexer may send a response to searchhead 804 either including event results or indicating that the indexerhas zero event results satisfying the search criteria based on thegeneration information. The response from each indexer may furtherinclude metadata information indicating an amount of time that elapsedto process the search and/or other diagnostic information. If a searchhead 804 does not receive a response from one or more of the indexers towhich the search query was distributed, the search head 804 may generatean alert indicating that a response was not received from the indexer(s)and that the search results therefore may be incomplete.

Typically, a search head 804 performs a search query with respect to themost recent generation created by the master node. However, in somecases where one or more queries take an abnormally long time to process,it is possible that indexers of a cluster could be processing a searchquery based on a generation that is earlier than the current generation.Those same indexers could receive a subsequent search query that isbased on the current generation and therefore concurrently process twoseparate queries based on different generations.

In one embodiment, a master node 806 may be configured to maintain anapproximately equal number of buckets on each indexer, and to maintainan approximately equal number of buckets for which each indexer hasprimary responsibility. Without an even distribution of buckets andprimary indexer responsibilities, it may be possible that individualindexers have primary responsibility for more buckets than others andmay become overloaded if a sufficiently large number of queries aresubmitted near in time to one another. A master node 806 mayperiodically rebalance buckets by determining how many buckets arecurrently stored by each indexer and which indexers are primary indexersfor each bucket, and create a new generation where the number of bucketsfor which each indexer has primary responsibility is approximately thesame.

FIG. 9 illustrates a flowchart of a process 900 that indexers may use toreplicate data in a clustered data intake and query system, according toan embodiment. At block 902, an indexer (e.g., one of indexers802A-802C) receives data from a forwarder 801. At block 904, the indexerprocesses and stores data in a corresponding data store 803A-803C.Processing the data by an indexer, for example, may include one or moreof the steps of segmenting, transforming, and indexing the data, asdescribed above. As indicated above, the data may be stored by theindexer in a data store in one or more grouped subsets, or buckets, ofthe data received from the forwarder.

At block 906, the indexer registers any newly created buckets withmaster node 806. Master node 806 may store information about the newlycreated buckets as part of the current generation information, or themaster node 806 may create a new generation that includes informationfor the newly created buckets. The master node 806 generates, based on aconfigured data replication policy for the cluster, data replicationinstructions that include a list of “peer” indexers in the cluster thatare to store a replicated copy of the one or more registered buckets. Asindicated above, the number of peer indexers that are selected to storea replicated copy of the one or more registered buckets correspond to areplication factor configured for the cluster. The selection ofparticular peer indexers for storing replicated bucket copies may befurther based in part on load balancing criteria or other factorsdetermined by the master node 806. The data replication instructions mayalso include, for each of the selected peer indexers, whether the peerindexer is to store a searchable or non-searchable copy of each bucket.The master node 806 sends the data replication instructions to theindexer registering the buckets.

In block 908, the indexer receives the data replication instructionsincluding the list of peer indexers to store replicated copies of thebuckets created by the indexer. In block 910, the indexer forwards thedata to the peer indexers, each of which stores the data in acorresponding data store and, if the peer indexer is storing asearchable copy, processes the data to generate a separate key wordindex. The data forwarded to the peer indexers may include the raw datareceived from the forwarder, the event data as processed by the indexer,or any combination thereof.

Referring again to FIG. 8 , to illustrate one example of a cluster withdata stored according to a data replication policy, each of data stores803A-803C is depicted storing one or more of the buckets labeled 1A, 2A,1B, 2B, 3A, and 3B. The example cluster 800, for example, may beconfigured with a replication factor of two (2). As indicated above, an“A” version of a bucket represents an original version of the bucket,whereas a “B” version represents a replicated copy of the same databucket. For example, indexer 802A may have received data from aforwarder 801 which indexer 803A processed and stored in the bucketlabeled 1A. After registering the bucket 1A with master node 806 andbased on received data replication instructions, indexer 802A forwardedthe data for bucket 1A to indexer 802B which stored a copy of the datain the bucket labeled 1B. Similarly, indexer 802C may have received datafrom a forwarder 801 and stored the data in the bucket labeled 3A. Basedon replication instructions received from master node 806, indexer 802Cforwarded the data for bucket 3A to indexer 802A which stored a copy ofthe data in the bucket labeled 3B.

Because the example data replication policy for cluster 800 isconfigured with a replication factor of two (2), as illustrated above,two copies of each bucket are stored by separate components of thecluster. In this manner, if any one of indexers 802A-802B were toexperience a failure, at least one copy of each bucket in the clusterstill exists somewhere in the cluster. In response to such a failure,master node 806 may create a new generation that, if necessary,reorganizes the designation of particular indexers in cluster 800 as theprimary indexer for each bucket so that a searchable copy of each bucketis available without disruption. Techniques for managing data in acluster environment are described in U.S. patent application Ser. No.13/648,116, filed on Oct. 9, 2012, U.S. patent application Ser. No.13/662,358, filed on Oct. 26, 2012, and U.S. Provisional PatentApplication No. 61/647,245, filed on May 15, 2012, each of which ishereby incorporated by reference in their entirety for all purposes.

3.0 Multi-Site Clusters

As indicated above, a cluster may be configured to replicate data in thecluster across multiple indexers of the cluster to improve theavailability of the data and to provide for disaster recovery of data inthe cluster. However, if all of the indexers of a cluster aregeographically collocated at the same site (e.g., within a single datacenter or office building), the benefits of data replication may benegated upon the occurrence of a failure that affects the entire site.For example, a site-wide failure caused by a major power outage, naturaldisaster, or a man-made disaster may be capable of entirely disruptingthe operation of a cluster if all of the cluster components are locatedat the same site.

In one embodiment, to further improve the fault tolerance and disasterrecovery abilities of a clustered data intake and query system, acluster may be configured to ensure that replication of data occursacross indexers located at multiple geographically dispersed sites. Acluster that includes the concept of “sites” as part of its datareplication policy is referred to herein as a multi-site cluster. A sitemay refer to a logical grouping of one or more cluster components thatmay each be associated with a particular geographic location. Forexample, if a business has two data centers on the east coast and westcoast, respectively, a user may define a separate site for each of thedata centers and associate particular cluster components with each sitedepending on where each of the cluster components is located physically.

In one embodiment, in addition to a user configurable replicationfactor, a data replication policy for a multi-site cluster may furtherinclude configuration of a site replication factor. Whereas areplication factor indicates a number of times that each bucket createdin a cluster is to be replicated within the cluster, a site replicationfactor indicates, for each bucket, a number of different sites at whichto store a copy of the bucket. For example, a cluster may be configuredwith five (5) separate sites, a replication factor of four (4), and asite replication factor of three (3). In this example, for each bucketcreated by an indexer of the cluster, three additional copies of thebucket are to be stored in the cluster, and the four total copies of thebucket are to be stored across at least three different sites of thefive sites. In this manner, by configuring a site replication factor ofat least two (2) for a multi-site cluster, the cluster may be able towithstand a failure of one or more entire sites.

FIG. 10 illustrates an example of a multi-site cluster that includes twodefined sites: a site 1000 and a site 1002. As indicated above, each ofthe sites 1000 and 1002 may represent an individual data center, officebuilding, or other location that houses one or more components of themulti-site cluster. Each of indexers 1004A-1004B, data stores 1006A,1006B and a search head 1008A is associated with site 1000. Each ofindexer 1 004C, data store 1 006C, master node 1010 and search head1008B is associated with site 1002. Two sites are illustrated in FIG. 10for the purposes of illustrating a clear example; however, a multi-sitecluster generally may include any number of sites, and any number ofcluster components associated with each site, depending on a particularimplementation and a particular user configuration. Although notdepicted, each of the indexers 1004A-1004C, data stores 1006A-1006C,master node 1010, and search heads 1008A-1008B may be connected via oneor more networks. The networks connected to the cluster components maybe implemented by any medium or mechanism that provides for the exchangeof data between components of the system. Examples of networks that mayconnect the components of multi-site cluster include, withoutlimitation, a network such as a Local Area Network (LAN), Wide AreaNetwork (WAN), wireless network, the Internet, Intranet, Extranet, etc.Any number of components within the multi-site cluster may be directlyconnected to each other through wired or wireless communicationsegments.

FIG. 11 illustrates a flowchart of a process 1100 that indexers may useto replicate data in a multi-site clustered data intake and querysystem, according to embodiments. In block 1102, an indexer (e.g., oneof indexers 1 004A-1 004C) receives data from a forwarder. At block1104, the indexer processes and stores the data in a corresponding datastore 1006A-1006C. For example, the indexer processing and storing thedata may include one or more steps of segmenting, transforming, andindexing the data, as described above.

At block 1106, the indexer registers any newly created buckets withmaster node 1010. As depicted in FIG. 12A, in a multi-site cluster,master node 1010 may be located at the same site as an indexer, or maybe located at a different site. However, in one embodiment, a multi-sitecluster includes only one master node 1010. Based on multi-site datareplication policy information, master node 1010 determines one or more“peer” indexers within the cluster to store replicated copies of thenewly created buckets registered by the indexer. As indicated above, theselected peer indexers may include one or more indexers that areassociated with sites that are different from the indexer registeringthe newly created buckets, depending on a configured site replicationfactor. The indexer may also receive instructions (e.g., generationinformation, etc.) indicating whether the indexer has primaryresponsibility for searching each bucket stored by the indexer.

At block 1108, the indexer obtains multi-site data replicationinstructions from master node 1010. At block 1110, the indexer sends thedata to the peer indexers selected by the master node including at leastpeer one indexer located at a different site, assuming that a sitereplication factor of at least two (2) is configured.

To illustrate a particular example of a data replication policy for amulti-sigh cluster, in FIG. 10 each of data stores 1006A-1006C isillustrated as storing one or more of the buckets labeled 1A, 2A, 1B,2B, 3A, and 3B. In the example of FIG. 10 , the multi-site cluster maybe configured with a multi-state data replication policy that specifiesa replication factor of two (2), and is further configured with a sitereplication factor of two (2). In other words, the example datareplication policy configured for the multi-site cluster indicates thateach bucket created by an indexer 1 006A-1 006C is replicated to atleast one other indexer, and further, that each bucket is replicated toan indexer that is located at a different site. The “A” and “B” versionsof a bucket represent copies of the same bucket.

For example, indexer 1004A may have received data from a forwarder whichindexer 1 004A processed and stored in bucket 1A. After registeringbucket 1A and based on replication instructions received from masternode 1010, indexer 1 004A forwarded the data for bucket 1A to peerindexer 1 004C which stored a copy of the data as bucket 1B. in theexample of FIG. 10 , because the data replication policy specifies asite replication factor of two (2), indexer 1004B is not available as areplication target for bucket 1A since creating a copy of bucket 1A atindexer 1004B would not result into copies of bucket 1A at two differentsites. As another example, indexer 1004C may have received data from aforwarder which indexer 1004C processed and stored in the bucket labeled3A. After registering the 3A bucket and based on received replicationinstructions, indexer 1004C forwarded the data for bucket 3A to indexer1 004B which stored a copy of the data in the bucket labeled 3B.

The example illustrated in FIG. 10 is only one particular example of adata replication policy for a multi-sigh cluster and otherconfigurations may be possible. As another example, replicated storageof buckets in a multi-sigh cluster may be configured in an asymmetricfashion where one site is responsible for storing all primary copies ofdata and another site is configured as a backup data center. In thiscase, one may configure the policy so that all but one copy lives on theprimary site and the remaining copies on the secondary site.

FIG. 11A illustrates a flowchart of a process 1101 that search heads mayuse to conduct queries in a multi-site clustered data intake and querysystem, according to embodiments. The illustrated flowchart includes twocolumns, one labeled “First Cluster” and the other labeled “SecondCluster.” This is to designate which entities perform which operationsof the method. In addition, each cluster is also capable of performingacts that are illustrated to be performed by the other cluster.

At block 1103, the search head receives a search query. At block 1105,the search head or an entity on behalf of the search head contacts amaster node in one or more clusters to ascertain active indexers forconducting a search, and a generation identifier associated with thesearch. In at least some embodiments, this step can be performed bycontacting the master node(s) through a firewall that exists between thesearch head and the master node(s). Examples of how this can be done areprovided below.

At block 1107, a master node in the second cluster receives, through itsfirewall, a request from the first cluster that requests the cluster'sactive indexers and a generation identifier associated with the search.At block 1109, the master node prepares a response including a list ofactive indexers and a generation identifier. At block 1111, the masternode sends the response to the first cluster.

At block 1113, the search head obtains, from the master node(s), thelist of active indexers and a generation identifier. At block 1115, thesearch head distributes the search query to all active indexers in thesecond cluster (as well as any additional clusters that might haveactive indexers), along with the generation identifier. This enables theactive indexers to conduct the search query as appropriate. At block1117, the search head receives a response from individual indexers thatincludes event results associated with the search query. The search headcan then process the event results as described above.

4.0 Site-Based Search Affinity

As indicated above, a multi-site cluster may be configured to replicatedata stored by the cluster across indexers located at multiplegeographically dispersed sites to increase the fault tolerance of thecluster against site-wide failures, among other benefits. As discussedearlier, a multi-site cluster may include multiple sites that eachlogically group one or more components of the cluster. For example, thecomponents of a multi-site cluster may include one or more search headsand which may be located at one or more of the sites. Because data in amulti-site cluster, and primary responsibility by indexers for thatdata, may be distributed across indexers located at a number ofdifferent sites, a search head may distribute search queries and receiveresults from indexers located at multiple sites. However, thedistribution of search queries to indexers located at multiplegeographically dispersed sites may introduce undesirable latency intothe search process that is not present when a search head is co-locatedwith all of the indexers of a cluster.

To reduce network traffic and latency when performing searches on datathat is stored by indexers located at multiple sites, in one embodiment,a multi-site cluster may be configured such that indexers that areco-located with a search head from which a search query originates aremore likely to return any search results that satisfy the query. Tocause indexers that are collocated with a search head to be more likelyto return search results for queries originating from that search head,in one embodiment, each indexer may store “search affinity” information.Search affinity information indicates, for each bucket stored by aparticular indexer and for each site from which a query may originate,whether the particular indexer has primary responsibility for returningsearch results for that bucket for searches originating at search headswithin that site. In other words, whether a given indexer has primaryresponsibility for returning search results for a particular bucket maydepend on the site from which the query originated, and the searchinfinity information may indicate this for the particular bucket foreach possible site from which the query may originate. Search affinityinformation for a multi-site cluster may be created and maintained by amaster node for the cluster, similar to generation information, and maychange over time as conditions within the cluster change, as describedherein.

In one particular embodiment, search affinity information may berepresented by a collection of bitmasks, where each bitmask of thecollection is associated with an indexer/bucket pair. For eachparticular indexer/bucket pair, a bitmask may provide an encodedrepresentation indicating zero or more sites of query origination forwhich the particular indexer has primary responsibility for respondingto search queries for that bucket. For example, a search affinitybitmask may be represented as a string of binary digits, where eachindividual digit in the string indicates to an indexer whether theindexer has primary responsibility for a bucket for searches originatingfrom a particular site.

As one example, a particular multi-site cluster may consist of three (3)separate sites identified by a number: site 1, site 2, and site 3. Toindicate for a particular indexer-bucket pair that the indexer hasprimary responsibility for the bucket for searches originating from siteN, a bitmask may be formed with a value of 1 at the 2^(N) position inthe binary string. For example, if a master node determines that anindexer X is to have primary responsibility for a bucket Y for searchesoriginating from site 1 (for example, because indexer X is also locatedat site 1), the master node may generate a bitmask for the indexerXbucket Y pair with a 1 in the 21 position (0010). Similarly, if indexerX is to have primary responsibility for bucket Y for searchesoriginating from site 2, the master node may generate a bitmask for theindexer X-bucket Y pair with a 1 in the 2² position (0100), and soforth. If a particular indexer-bucket pair is not to have primaryresponsibility for searches originating from any site, a master node maygenerate a bitmask of all zeroes (0000) for the particularindexer-bucket pair.

Although the examples above illustrate bitmasks that indicate that anindexer has primary responsibility for a bucket for searches originatingfrom only a single site, a search affinity bitmask may indicate that anindexer has primary responsibility for a particular bucket for searchesoriginating from multiple sites. For example, an indexer X-bucket Y pairmay be associated with a bitmask of 0110, indicating that indexer X hasprimary responsibility for bucket Y for searches originating from eithersite 1 or site 2. In general, any combination of search affinitybitmasks may be configured depending on the characteristics of aparticular cluster and/or a user configuration.

In an embodiment, search affinity information may be created by a masternode and distributed to each indexer of a multi-site cluster for storageby the indexers, similar to distribution of bucket generationinformation for clusters. Also similar to bucket generation information,search affinity information may change over time as conditions withinthe cluster change and successive iterations of the search affinityinformation may be identified by generation identifiers. For example,first search affinity information created by a master node may beidentified by a label “generation 0”, second search affinity informationmay be identified by a label “generation 1”, and so forth. A master nodemay create new generations of search affinity information andcorresponding generation identifiers in response to a number ofdifferent cluster events including, but limited to, any of: the masternode initializing, a new indexer joining the cluster, a current indexerfailing or leaving the cluster, to rebalance the buckets of a cluster,etc. Indexers may store multiple generations of search affinityinformation.

In an embodiment, when a search head distributes a search query toindexers of a cluster, the search head may also send a site identifierwhich indicates the site at which the search head is located. The searchhead may also distribute a generation identifier that identifiesparticular search affinity information stored by the indexers. In thismanner, when an indexer receives a search from a particular search head,the indexer may use the site identifier and the search affinityinformation identified by the generation identifier to determine, foreach bucket stored by the indexer, whether the indexer has primaryresponsibility for searches originating from the site identified by thesite identifier.

FIG. 12A illustrates an example block diagram of a multi-site clustereddata intake and query system that is configured to process searchrequests based on search affinity information, according to anembodiment. In FIG. 12A, a multi-site cluster 1150 includes a site 1152and a site 1154. Each of sites 1152, 1154 includes one or more of thecluster components including indexers 1156A-1156C, data stores11158A-1158C, search heads 1160A, 1160B, and a master node 1164.

Each of indexers 1156A-1156C is depicted as storing one or more of thebuckets labeled 1A, 1B, 1C, 2A, 2B, and 2C in a corresponding data store1158A-1158C. Similar to the examples described above, an “A”, “B”, and“C” version of a bucket represent replicated copies of the same bucket.In the example of FIG. 12A, the multi-site cluster 1150 may beconfigured with a replication factor of three (3) and a site replicationfactor of two (2). Thus, for example, three separate copies of each ofbuckets 1 and 2 exist in the cluster and at least two separate copies ofeach bucket are stored at two different sites.

In FIG. 12A, each of data stores 1158A-1158C is illustrated as storingsearch affinity information 1162. The search affinity information 1162may have been received and stored by each indexer, for example, when theindexers 1156A-1156C registered the created buckets with master node1162, periodically received from master node 1164, and/or the searchaffinity information 1162 may be included as part of a search querydistributed by search head 1160A. As indicated above, in one embodiment,the search affinity information may include a collection of bitmasks foreach indexer-bucket pair where each digit of a bitmask representswhether the indexer has primary responsibility for the bucket forsearches originating from a particular site. In FIG. 12A, only thosesearch affinity identifiers relevant to each indexer are illustrated ineach of the data stores 1158A-1158C; however, each indexer may receiveand store search affinity identifiers for the entire cluster, or onlythose search affinity identifiers that are associated with bucketsstored by the particular indexer.

FIG. 12B is a flowchart 1180 of a process that a search head andindexers of a multisite cluster may perform during a search queryaccording to search affinity information. In block 1182, a search head(e.g., search head 1160A or 1160B) receives a search request from aclient. In block 1184, the search head distributes the query and a siteidentifier to indexers (e.g., indexers 1156A-1156C) of the multi-sitecluster. The site identifier indicates the site at which the search headdistributing the query is located. The site identifier may be includedwith the query, or may be sent separately. The search head may also senda generation identifier that identifies particular search affinityinformation for the indexers to use when processing the query. Forexample, the indexers may store multiple generations of search affinityinformation and the generation identifier may identify a particulargeneration of search affinity information to use for the query.

In block 1186, based on the query, search affinity information, and thesite identifier, each of the indexers to which the query was distributedsearches a corresponding data store for event results responsive to thequery. As indicated above, each indexer may store search affinityinformation that indicates, for each bucket stored by the indexer,whether the indexer has primary responsibility for the bucket forsearches originating from particular sites. The indexers may use thesite identifier sent by the search head to determine the originatingsite of the query for comparison to the search affinity information. Forexample, if an indexer receives a query and a site identifier indicatingthat the originating search head is at site 2, the indexer may searchbuckets that are associated with a bitmask with a 1 in the 22 position(0010).

In block 1188, the search head combines or reduces all of the partialresults or events received from the indexers together to determine afinal result responsive to the query.

Referring again to FIG. 12A, search head 1160A may distribute a searchquery to indexers 1156A-1156C and include with the query a siteidentifier of 1. When indexer 1156A receives the search query fromsearch head 1160A, indexer 1156A may consult search affinity information1162 to determine whether indexer 1156A stores any buckets associatedwith a bitmask having a value of 1 in the 2¹ position (010). Forexample, indexer 1156A may determine that bucket 1A is associated with abitmask having a 1 in the 2¹ position. Thus, in response to the queryfrom search head 1160A, indexer 1156A may return one or more eventresults from bucket 1A if any of the data in bucket 1A is responsive tothe search query. Similarly, because bucket 2B is associated with abitmask that includes a 0 in the 2¹ position, indexer 1156A does notreturn any results from bucket 2B, even if bucket 2B contains eventresults that are responsive to the query.

5.0 Cloud Based Clusters

In one embodiment, in order to further improve the fault tolerance anddisaster recovery abilities of the clustered data intake and querysystem, cloud-based clusters are utilized. A cloud-based cluster can bethought of as a thirdparty, managed data intake and query system. Thecloud-based cluster can reside in the form of a hosted web service,managed by a third-party, which is accessible through the cloud. So, ina typical deployment, an organization may have an “onpremises” dataintake and query system, such as that described above. In addition, theorganization may also have or otherwise make use of one or morecloud-based clusters that utilize the principles described above andbelow. Collectively, the “on-premises” and cloud-based clusters arereferred to as a “hybrid” system.

The use of cloud-based clusters carries with it a number of differentadvantages.

For example, consider the notion of “bursting”. That is, an organizationmay have an on-premises deployment and encounter a situation where anunusually large volume of data is to be processed. The volume of thedata may be such that the on-premises deployment may not be able toadequately process the data. In this instance, cloud-based clusters canbe utilized to scale out and complement the on-premises deployment inthe cloud, without having to incur the cost of adding additionalhardware and software infrastructure to the on-premises deployment.

Another advantage concerns data isolation. Specifically, there areparticular types of data which, because of the nature of the data or forlegal reasons, it is more desirable to maintain the data in on-premisesenvironment. For example, sensitive data such as personal information,Social Security numbers, addresses, financial information, and the like,may be desirable to maintain m the on premises environment. There mayalso be data such as sensitive or highly confidential corporateinformation which is desired to be maintained in the on premisesenvironment. Yet, there may exist other data, such as various data logsand the like, that does not have stringent requirements for security.This data may be better suited for residing in the cloud. In thisinstance, it may be advantageous to maintain some data in theon-premises environment, and maintain other data in the cloud cluster.

Further, consider a situation where a corporation has a primary, onpremises deployment. The corporation may have other teams outside of thepremises that desire to use the data intake and query system. Ratherthan having these other teams deploy their own system with perhaps itsown licensing model, using a cloud-based cluster to complement theon-premises deployment may be more desirable in terms of utilizing thesame operational parameters, e.g., the same licensing model and thelike.

In addition, cloud-based clusters can provide desirable economicadvantages for organizations that may not necessarily have the financialresources, budget, and time to add the additional hardwareinfrastructure to support a scaled deployment of its on-premisesdeployment. So in this instance, the end-user may wish to scale or growtheir license, but may not necessarily wish to incur increased costsassociated with the hardware infrastructure.

An additional advantage of using cloud-based clusters includes the factthat a large amount of data that can be processed in accordance with thetechniques described herein may likely already reside in the cloud.Accordingly, by using cloud-based clusters in concert with on-premisesdeployments, the expense of retrieving the cloud-based data for uselocally is virtually eliminated.

Further, advantages of cloud-based clusters include the fact that manycorporations are now moving to cloud-based environments for their data.By having a hybrid solution that utilizes both an on-premises deploymentand a cloud based cluster, these corporations and other users cansmoothly transition to a solely cloud-based environment by graduallyphasing out their on-premises deployment.

In at least some embodiments, a search head in one cluster, e.g. an “onpremises” cluster, may not necessarily know the topology of the othercluster, e.g. a cloud-based cluster, in terms of conducting a particularsearch query. In this case, the search head can communicate with theother cluster to request information associated with the other cluster'stopology. This information can include information associated with howto communicate with particular indexers. By way of example and notlimitation, such information can include the IP addresses of theindexers that are to be used for a particular search query. Once thesearch head receives information from the other cluster, it can thensend out its search query or otherwise cause its search query to be sentto the other cluster from its own cluster.

In at least some embodiments, the search head can communicate with theother cluster through the other cluster's firewall. That is, the othercluster's firewall can be configured with rules that allow the searchhead to send requests through to the cluster. For example, the othercluster's firewall may be configured with the rule that indicates that asearch head having a particular IP address (or communications on behalfof a search head having a particular originating IP address in the eventa gateway is used) is allowed to send requests to the cluster asking forinformation associated with the indexers on which to conduct aparticular search query. Examples of how this can be done are providedbelow.

FIG. 13 illustrates a flowchart of a process 1300 that search heads mayuse to conduct queries in a multi-site clustered data intake and querysystem, according to embodiments. The illustrated flowchart includes twocolumns, one labeled “On-Premises Cluster” and the other labeled“Cloud-Based Cluster.” This is to designate which entities perform whichoperations of the method. In addition, each cluster is also capable ofperforming acts that are illustrated to be performed by the othercluster.

At block 1302, the search head receives a search query. At block 1304,the search head contacts one or more other clusters to requestinformation associated with active indexers. This communication may ormay not occur through firewalls on the other clusters. In at least someembodiments, this can occur through a firewall of the cloud-basedcluster.

At block 1305, the cloud-based cluster receives a request forinformation associated with active indexers of the cluster. At block1307, the cloud-based cluster prepares a response including informationassociated with its active indexers. This information will allow theon-premises cluster to communicate with the cloud-based cluster forpurposes of conducting a search. At block 1309, the cloud-based clustersends the response to the on-premises cluster.

At block 1306, the search head obtains, from the cloud-based cluster,the information associated with active indexers of the cloud-basedcluster. In at least some embodiments, this information can include alist of active indexers and a generation identifier. At block 1308, thesearch head distributes the search query to all active indexers, in eachcluster, in accordance with the information received from thecloud-based cluster, e.g., the generation identifier. In at least someembodiments, this can occur through the cloud-based clusters's firewall.At block 1310, the search head receives a response from individualindexers that include event results associated with the search query.

FIG. 14 illustrates an example of a multi-cluster configuration thatprovides but one example of how the process described just above can beaccomplished. The multi-cluster configuration includes two clusters:cluster 1400 and a cloud-based cluster 1402 that resides in the cloud1414. Cluster 1400 includes indexers 1404A, 1404B, corresponding datastores 1406A, 1406B, and a search head 1408A. Similarly, cluster 1402includes indexers 1404C, 1404D, corresponding data stores 14006C, 1406D,and a search head 1408B. Also depicted are data sources designated “S”which provide data to each of the clusters. The illustrated clusters areconnected by way of the cloud 1414. In this particular example, eachcluster includes a firewall as depicted.

In the illustrated and described example, the firewall at thecloud-based cluster 1402 is configured with a rule set that allowsinbound communication from a particular IP address associated withcluster 1400. The particular IP address can be any suitable IP addresssuch as, by way of example and not limitation, the IP address of thesearch head, an originating IP address that is different from the IPaddress of the search head, and the like. An originating IP address maybe one that is associated with a gateway in the event that cluster 1400utilizes a gateway to communicate with cluster 1402.

The firewall at cluster 1400 is configured with a rule set that allowsoutbound communication from the cluster 1400. The rule set can specifythat outbound communication is allowed based on an IP address associatedwith cluster 1400 (such as the IP address of the search head 1408A, anoriginating IP address, and the like) and the port associated withcluster 1402 with which a connection is desired. The firewall at cluster1400 can also provide a blocking function that blocks incoming requestsuntil its rule set is modified to allow specific kinds of requests.Thus, the firewall on cluster 1400 can be configured to only allowoutgoing requests, and the firewall on cluster 1402 can be configured toallow incoming requests associated with cluster 1400.

FIG. 15 illustrates a flowchart of a process 1500 that search heads mayuse to conduct queries in a cloud-based data intake and query system,according to embodiments. The illustrated flowchart includes twocolumns, one labeled “On Premises Cluster” and the other labeled“Cloud-Based Cluster.” This is to designate which entities perform whichoperations of the method. In addition, each cluster is also capable ofperforming acts that are illustrated to be performed by the othercluster.

At block 1502, the search head receives a search query. At block 1504,the search head or an entity on behalf of the search head communicates,with a cloud based cluster through the cluster's firewall, to requestinformation on how to communicate with active indexers.

At block 1505, the cloud-based cluster receives, through its firewall,the request for information on how to communicate with the cloud-basedcluster's active indexers. At block 1507, the cloud-based clusterprepares a response including the information on how to communicate withthe active indexers. At block 1509, the cloud-based cluster sends theresponse to the on-premises cluster.

At block 1506, the search head at the on-premises cluster obtains, fromthe cloud-based cluster, the information on how to communicate with theactive indexers. In at least some embodiments, this information caninclude a list of active indexers including the indexers' respective IPaddresses, and a generation identifier as described above. At block1508, the search head distributes the search query to all activeindexers, in each cluster, including the cloud-based cluster, inaccordance with the information received from the cloud-based cluster,e.g., the generation identifier. This can also include distributing thesearch query to its own active indexers. This enables the activeindexers (at both the on-premises cluster and the cloud-based cluster)to conduct the search query as appropriate. At block 1510, the searchhead receives a response from individual indexers that includes eventresults associated with the search query. The search head can thenprocess the event results as described above.

FIG. 16 illustrates an example of a system that includes a cloud-basedcluster. Specifically, the system includes an “on-premises” cluster 1600and a cloud-based cluster 1602. Each cluster can include the componentsdescribed above. Specifically, cluster 1600 includes indexers 1604A,1604B, corresponding data stores 1606A, 1606B, a search head 1608A and amaster node 161 OA. Similarly, cloud-based cluster 1602 includesindexers 1604C, 1604C, corresponding data stores 1606C, 1606C, a searchhead 1608B and a master node 1610B.

Each of the clusters includes a firewall as illustrated. The firewallsoperate as described above with respect to FIG. 14 .

Also depicted are data sources designated “S” which provide data to eachof the clusters. Although not depicted, each of the indexers, datastores, master nodes, and search heads may be connected via one or morenetworks. The networks connected to the cluster components may beimplemented by any medium or mechanism that provides for the exchange ofdata between components of the system. Examples of networks that mayconnect the components of the multi-cluster configuration include,without limitation, a network such as a Local Area Network (LAN), WideArea Network (WAN), wireless network, the Internet, Intranet, Extranet,etc. Any number of components within the clusters may be directlyconnected to each other through wired or wireless communicationsegments.

FIG. 17 illustrates a flowchart of a process 1700 that search heads mayuse to conduct queries in a cloud-based data intake and query system,according to embodiments. The illustrated flowchart includes twocolumns, one labeled “On Premises Cluster” and the other labeled“Cloud-Based Cluster.” This is to designate which entities perform whichoperations of the method. In addition, each cluster is also capable ofperforming acts that are illustrated to be performed by the othercluster.

At block 1702, the search head receives a search query. At block 1704,the search head or an entity on behalf of the search head communicates,with a master node in a cloud-based cluster through the cluster'sfirewall, to request information on how to communicate with activeindexers.

At block 1705, the master node in the cloud-based cluster receives,through the cluster's firewall, the request for information on how tocommunicate with the cloud-based cluster's active indexers. At block1707, the master node prepares a response including the information onhow to communicate with the active indexers. At block 1709, the masternode of the cloud-based cluster sends the response to the on-premisescluster.

At block 1706, the search head obtains, from the master node, a list ofactive indexers and a generation identifier. In at least someembodiments, the list of active indexers including the indexers'respective IP addresses. At block 1708, the search head distributes thesearch query to all active indexers, in each cluster, including thecloud-based cluster, in accordance with the information received fromthe cloud-based cluster, e.g., the generation identifier. This can alsoinclude distributing the search query to its own active indexers aswell. This enables the active indexers to conduct the search query asappropriate. At block 1710, the search head receives a response fromindividual indexers that includes event results associated with thesearch query. The search head can then process the event results asdescribed above.

Having considered the notion of cloud-based clusters, consider now thenotion of configuration information and how configuration informationcan be shared between various clusters including cloud-based clusters.

6.0 Sharing Configuration Information

Configuration information can be thought of as information that providesadditional knowledge that can be utilized during a search. Examples ofconfiguration information can include, by way of example and notlimitation, saved searches, event types, transactions, tags, fieldextractions, field transforms, lookups, workflow actions, searchcommands, and views.

A saved search is a search the user has made available for later use. Inat least some embodiments, searches can be saved as reports, alerts, ordashboard panels. An event type enables categorizing and labeling of allindexed events that match a specified search string. An event type has aname and an associated search. A transaction is a group ofconceptually-related events that spans time. Events grouped together bytransaction often represent a complex, multistep business-relatedactivity, such as all events related to a single hotel customerreservation session, or a customer session on a retail website. A tagenables efficient searches for events that contain particular fieldvalues. One or more tags can be assigned to any field/value combinationincluding event types, hosts, sources, and source types. Tags can enableone to track abstract field value such as IP addresses or ID numbers.For example, one could have a number of field values related to ahome-office, including an IP address such as 192.168.1.2. These valuescould be tagged as “home office” and then search on tag=homeoffice tofind all events with field values that have the homeoffice tag. Tagsalso enable grouping of sets of related field values together. Inaddition, multiple tags can be given to extract fields that reflectdifferent aspects of their identity. This enables creation of tag-basedsearches that use Boolean operators to narrow down on specific eventsets. A field extraction is a field that has been extracted from theevent data. A field transformation contains a field-extracting regularexpression and other attributes to govern the way that the transformextracts and formats field/value pairs. A lookup enables the addition offields and related values to search results based on field matching witha suitable table or script. For example, one can use a lookup to performDNS or reverse DNS lookups on IP addresses or host names within data. Aworkflow action enables a variety of interactions between indexed fieldsin events and other web resources, including external web resources. Forexample, workflow actions can be defined that are associated with an IPaddress field in search results. They can be used to perform an externallookup based on a particular value of that field in a specified event. Asearch command is a command that is utilized to interact with data.Search commands can be used to refine and modify search results. A viewconstitutes or defines a way in which search results are displayed.These constitute but a few examples of configuration information. Othertypes of configuration information can be utilized without departingfrom the spirit and scope of the claimed subject matter.

In the illustrated and described embodiments, particularly in the cloudbased cluster embodiments, configuration information can be sharedamongst the clusters. This permits different clusters to benefit fromconfiguration information that might have been developed relative to adifferent cluster. In the illustrated and described embodiments,configuration information can be shared by using a shared data store.That is, each cluster can communicate its configuration informationoutside of the cluster to a data store in which the shared configurationinformation resides. This can include communicating the configurationinformation through a firewall associated with the cluster and to theshared data store. One reason for communicating the configurationinformation through the firewall and outside the cluster is forsecurity. Specifically, it is a safer practice to not allow incomingconnections to a particular network associated with the cluster. Havingan outgoing connection to, for example, the shared data store is muchsafer because the outgoing connection can be controlled much moreeasily. As in the illustrated and described embodiment, the shared datastore can be implemented as “passive” storage. In this manner, the datafrom the shared data store is not directly accessed by the searchprocess from the shared location. Rather, a different process, such asone that can be located in each cluster, synchronizes the data from theshared storage to each cluster and back.

As an example, consider FIG. 18 which illustrates a system that issubstantially the same as described with respect to FIG. 16 , exceptthat the “16XX” series designators have been replaced by “18XX” seriesdesignators. Since the operation of the FIG. 18 system is substantiallythe same as the FIG. 16 system, a description of such operation has beenomitted for brevity. In addition, because of spacing constraints, thecloud within which cloud-based cluster 1802 would reside has beenremoved for clarity. It is to be appreciated and understood, however,that the cloud-based cluster 1802 resides within the cloud in the samemanner as set forth in FIG. 16 with respect to cluster 1602.

Assume in this example that cluster 1800, an “on-premises” cluster, hasdeveloped or otherwise modified some configuration informationassociated with a particular search. In this particular example, thecluster 1800 and, more accurately, the search head 1808A can cause theconfiguration information to be communicated through its associatedfirewall and deposited in the shared data store (designated “SharedConfiguration Information”). Now, if the cloud-based cluster 1802 wishesto utilize the configuration information, the cloud-based cluster 1802and, more accurately, search head 1808B, can retrieve or cause retrievalof the configuration information from that location. In this manner,there is no direct communication between the two clusters with respectto the configuration information. Again, this provides an added degreeof security and safety for each cluster.

In at least some embodiments, the configuration information can beconfigured as “read-only” information. In this manner, one cluster maynot modify configuration information provided by another cluster. In atleast some other embodiments, the configuration information can beconfigured as “read and write” information. In this manner, one clustermay modify configuration information provided by another cluster. Ininstances where configuration information can be modified by anothercluster, synchronization techniques can be utilized to resolve anyinconsistent changes that might be made by different clusters. This canbe done using any suitable type of synchronization technique. Forexample, one approach can be to ascertain the priority of a particularchange and merge higher priority changes into the configurationinformation. Other approaches can be used including various algorithmicapproaches that will be appreciated by the skilled artisan. Otherapproaches can include utilizing locks in which configurationinformation IS “locked” for purposes of making changes. Whenconfiguration information is locked, only the cluster that locked theconfiguration information can make changes. When the configurationinformation is unlocked, other clusters can be free to make changes tothe configuration information.

The configuration information can be organized and bundled in anysuitable way. In at least some embodiments, the configurationinformation represents a knowledge object. Accordingly, each type ofconfiguration information represents its own associated knowledgeobject. So, for example, saved searches represent saved search knowledgeobjects. Likewise, event types represent event type knowledge objects,and so on. Information and data of the knowledge objects can then beprovided by a search head to the shared data store as described above.

FIG. 19 illustrates a flowchart of a process 1900 that can be utilizedto share configuration information between clusters in a cloud-baseddata intake and query system, according to embodiments. The illustratedflowchart includes two columns, one labeled “Cluster” and the otherlabeled “Cloud-based cluster.” This is to designate which entitiesperform which operations of the method. In addition, each cluster isalso capable of performing acts that are illustrated to be performed bythe other cluster.

At block 1902, a first cluster creates or accesses configurationinformation associated with searching data accessible by the firstcluster. This can be done in any suitable way utilizing any suitabletype of configuration information, examples of which are provided above.In some embodiments, the configuration information includes a lookuptable for enriching data retrieved from a search query. In someembodiments, the configuration information includes schema for searchingdata. In some other embodiments, the configuration information includesextraction rules defining fields of a late binding schema for searchingdata.

At block 1904, the first cluster communicates the created theconfiguration information to a shared storage location. The sharedstorage location is shared between at least the first cluster and thecloud-based cluster for searching different data than the data in thefirst cluster. This can be done in any suitable way. For example, in atleast some embodiments, the first cluster communicates its createdconfiguration information through its firewall to the shared storagelocation. This communication can be done through on outgoing one-wayconnection from the first cluster

At block 1906, a second cluster, here illustrated as a cloud-basedcluster, retrieves or otherwise receives the configuration informationfrom the shared location. This can be done by the cloud-based clusterretrieving the configuration information from the shared storagelocation through an outgoing one-way connection. In embodiments, thecloud-based cluster can retrieve the configuration information from theshared storage location through a firewall associated with thecloud-based cluster. After the configuration information is retrieved, avalidation and sanitization process can take place to ensure that thedata does not contain malicious configurations or executables. At block1908, the cloud-based cluster uses the retrieved configurationinformation from the shared storage location to conduct a search. Thesearch can be a search of data that is different from data of the firstcluster. The data can include any suitable type of data examples ofwhich are provided above. Such data can include, by way of example andnot limitation, log data, wire data and the like. Further, as in theabove examples, the searches conducted by the first and second clusterscan use a late-binding schema as described above. The shared storage canbe assessable by other clusters as well.

If the configuration information is “read only”, then the method canterminate at block 1908. If, on the other hand, the configurationinformation is configured as “read and write” and the cloud-basedcluster (or whatever cluster retrieved the configuration information)modified the configuration information in some way, the method caninclude an additional step of communicating or causing communication ofthe configuration information back to the shared storage location. Thiscan include, in at least some embodiments, communicating theconfiguration information back to the shared storage location through afirewall associated with a cloud-based cluster.

The process just described eliminates the need for direct communicationbetween the clusters with respect to sharing configuration information.In this manner, only outgoing connections from each cluster are utilizedto provide the configuration information to a shared location from whichit can be retrieved and used by other clusters, thus promoting networksecurity.

Having considered various embodiments associated with sharingconfiguration information, consider now an example system and devicethat can be utilized to implement the described embodiments.

Example System and Device

FIG. 20 illustrates an example system generally at 2000 that includes anexample computing device 2002 that is representative of one or morecomputing systems and/or devices that may implement the varioustechniques described herein. This is illustrated through inclusion ofthe data intake and query module 2016, which operates as describedabove. The computing device 2002 may be, for example, a server of aservice provider, a device associated with a client (e.g., a clientdevice), an on-chip system, and/or any other suitable computing deviceor computing system.

The example computing device 2002 as illustrated includes a processingsystem 2004, one or more computer-readable media 2006, and one or moreI/O interface 2008 that are communicatively coupled, one to another.Although not shown, the computing device 2002 may further include asystem bus or other data and command transfer system that couples thevarious components, one to another. A system bus can include any one orcombination of different bus structures, such as a memory bus or memorycontroller, a peripheral bus, a universal serial bus, and/or a processoror local bus that utilizes any of a variety of bus architectures. Avariety of other examples are also contemplated, such as control anddata lines.

The processing system 2004 is representative of functionality to performone or more operations using hardware. Accordingly, the processingsystem 2004 is illustrated as including hardware elements 2010 that maybe configured as processors, functional blocks, and so forth. This mayinclude implementation in hardware as an application specific integratedcircuit or other logic device formed using one or more semiconductors.The hardware elements 2010 are not limited by the materials from whichthey are formed or the processing mechanisms employed therein. Forexample, processors may be comprised of semiconductor(s) and/ortransistors (e.g., electronic integrated circuits (ICs)). In such acontext, processor-executable instructions may beelectronically-executable instructions.

The computer-readable storage media 2006 IS illustrated as includingmemory/storage 2012. The memory/storage 2012 represents memory/storagecapacity associated with one or more computer-readable media. Thememory/storage component 2012 may include volatile media (such as randomaccess memory (RAM)) and/or nonvolatile media (such as read only memory(ROM), Flash memory, optical disks, magnetic disks, and so forth). Thememory/storage component 2012 may include fixed media (e.g., RAM, ROM, afixed hard drive, and so on) as well as removable media (e.g., Flashmemory, a removable hard drive, an optical disc, and so forth). Thecomputer-readable media 2006 may be configured in a variety of otherways as further described below.

Input/output interface(s) 2008 are representative of functionality toallow a user to enter commands and information to computing device 2002,and also allow information to be presented to the user and/or othercomponents or devices using various input/output devices. Examples ofinput devices include a keyboard, a cursor control device (e.g., amouse), a microphone, a scanner, touch functionality (e.g., capacitiveor other sensors that are configured to detect physical touch), a camera(e.g., which may employ visible or non-visible wavelengths such asinfrared frequencies to recognize movement as gestures that do notinvolve touch), and so forth. Examples of output devices include adisplay device (e.g., a monitor or projector), speakers, a printer, anetwork card, tactile-response device, and so forth. Thus, the computingdevice 2002 may be configured in a variety of ways as further describedbelow to support user interaction.

Various techniques may be described herein m the general context ofsoftware, hardware elements, or program modules. Generally, such modulesinclude routines, programs, objects, elements, components, datastructures, and so forth that perform particular tasks or implementparticular abstract data types. The terms “module,” “functionality,” and“component” as used herein generally represent software, firmware,hardware, or a combination thereof. The features of the techniquesdescribed herein are platform-independent, meaning that the techniquesmay be implemented on a variety of commercial computing platforms havinga variety of processors.

An implementation of the described modules and techniques may be storedon or transmitted across some form of computer-readable media. Thecomputer readable media may include a variety of media that may beaccessed by the computing device 2002. By way of example, and notlimitation, computer readable media may include “computer-readablestorage media” and “computer readable signal media.”

“Computer-readable storage media” may refer to media and/or devices thatenable persistent and/or non-transitory storage of information incontrast to mere signal transmission, carrier waves, or signals per se.Thus, computer-readable storage media refers to non-signal bearingmedia. The computer-readable storage media includes hardware such asvolatile and non-volatile, removable and non removable media and/orstorage devices implemented in a method or technology suitable forstorage of information such as computer readable instructions, datastructures, program modules, logic elements/circuits, or other data.Examples of computer-readable storage media may include, but are notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, digital versatile disks (DVD) or other optical storage, harddisks, magnetic cassettes, magnetic tape, magnetic disk storage or othermagnetic storage devices, or other storage device, tangible media, orarticle of manufacture suitable to store the desired information andwhich may be accessed by a computer.

“Computer-readable signal media” may refer to a signal-bearing mediumthat is configured to transmit instructions to the hardware of thecomputing device 2002, such as via a network. Signal media typically mayembody computer readable instructions, data structures, program modules,or other data in a modulated data signal, such as carrier waves, datasignals, or other transport mechanism. Signal media also include anyinformation delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communication media include wired media such as awired network or direct-wired connection, and wireless media such asacoustic, RF, infrared, and other wireless media.

As previously described, hardware elements 2010 and computer-readablemedia 2006 are representative of modules, programmable device logicand/or fixed device logic implemented in a hardware form that may beemployed in some embodiments to implement at least some aspects of thetechniques described herein, such as to perform one or moreinstructions. Hardware may include components of an integrated circuitor on-chip system, an application-specific integrated circuit (ASIC), afield-programmable gate array (FPGA), a complex programmable logicdevice (CPLD), and other implementations in silicon or other hardware.In this context, hardware may operate as a processing device thatperforms program tasks defined by instructions and/or logic embodied bythe hardware as well as a hardware utilized to store instructions forexecution, e.g., the computer-readable storage media describedpreviously.

Combinations of the foregoing may also be employed to implement varioustechniques described herein. Accordingly, software, hardware, orexecutable modules may be implemented as one or more instructions and/orlogic embodied on some form of computer-readable storage media and/or byone or more hardware elements 2010. The computing device 2002 may beconfigured to implement particular instructions and/or functionscorresponding to the software and/or hardware modules. Accordingly,implementation of a module that is executable by the computing device2002 as software may be achieved at least partially in hardware, e.g.,through use of computer-readable storage media and/or hardware elements2010 of the processing system 2004. The instructions and/or functionsmay be executable/operable by one or more articles of manufacture (forexample, one or more computing devices 2002 and/or processing systems2004) to implement techniques, modules, and examples described herein.

The techniques described herein may be supported by variousconfigurations of the computing device 2002 and are not limited to thespecific examples of the techniques described herein. This functionalitymay also be implemented all or in part through use of a distributedsystem, such as over a “cloud” 2014 via a platform 2016 as describedbelow.

The cloud 2014 includes and/or is representative of a platform 2016 forresources 2018. The platform 2016 abstracts underlying functionality ofhardware (e.g., servers) and software resources of the cloud 2014. Theresources 2018 may include applications and/or data that can be utilizedwhile computer processing is executed on servers that are remote fromthe computing device 2002. Resources 2018 can also include servicesprovided over the Internet and/or through a subscriber network, such asa cellular or Wi-Fi network.

The platform 2016 may abstract resources and functions to connect thecomputing device 2002 with other computing devices. The platform 2016may also serve to abstract scaling of resources to provide acorresponding level of scale to encountered demand for the resources2018 that are implemented via the platform 2016. Accordingly, in aninterconnected device embodiment, implementation of functionalitydescribed herein may be distributed throughout the system 2000. Forexample, the functionality may be implemented in part on the computingdevice 2002 as well as via the platform 2016 that abstracts thefunctionality of the cloud 2014. As such, cloud-based clusters such asthose described above can be provided by platform 2016.

In an embodiment, an apparatus comprises a processor and is configuredto perform any of the foregoing methods.

In an embodiment, a non-transitory computer readable storage medium,storing software instructions, which when executed by one or moreprocessors cause performance of any of the foregoing methods.

Note that, although separate embodiments are discussed herein, anycombination of embodiments and/or partial embodiments discussed hereinmay be combined to form further embodiments.

Having thus described the invention, what is claimed is:
 1. Acomputer-implemented method, comprising: determining, at a firstcluster, information identifying a plurality of indexers of the firstcluster based on a master node of the first cluster identifying activeindexers within the first cluster; transmitting, from the first clusterto a second cluster, the information identifying the plurality ofindexers, wherein the information identifying the plurality of indexerscomprises: a list of active indexers, and an indication of how tocommunicate with the plurality of indexers that is used by the secondcluster in distributing a distributed search query to the plurality ofindexers, the indication including Internet Protocol addressesassociated with the plurality of indexers; receiving, at the pluralityof indexers of the first cluster, the distributed search query from thesecond cluster, wherein the distributed search query is distributedacross the plurality of indexers based on the information identifyingthe plurality of indexers; and providing, at the first cluster, aresponse to the distributed search query from at least one of theplurality of indexers, wherein each response from a respective indexeris generated by the respective indexer based on an evaluation, by therespective indexer, of the distributed search query.
 2. The method asdescribed in claim 1, further comprising receiving, at the firstcluster, a request for the information identifying the plurality ofindexers of the first cluster through a firewall of the first cluster.3. The method as described in claim 1, wherein the transmitting of theinformation identifying the plurality of indexers is through a firewallof the second cluster.
 4. The method as described in claim 1, whereinthe first cluster is a cloud-based cluster and the second cluster is anon-premises cluster.
 5. The method as described in claim 1, wherein theevaluation is on events associated with time stamps, the eventscomprising raw portions of machine data.
 6. The method as described inclaim 1, wherein the distributed search query is configured to be usedwith a late-binding schema.
 7. The method as described in claim 1,wherein the evaluation is performed on log data.
 8. The method asdescribed in claim 1, wherein the first cluster includes a single masternode that includes information about the active indexers within thefirst cluster, and the information identifies the plurality of indexersbased on the single master node of the first cluster identifying theactive indexers.
 9. The method as described in claim 1, wherein thefirst cluster and the second cluster each include a single master nodethat includes information about the active indexers within itsrespective cluster, and the information identifies the plurality ofindexers based on the single master node of the first clusteridentifying the active indexers.
 10. The method as described in claim 1further comprising receiving, at the first cluster, a request for theinformation identifying the plurality of indexers of the first clusterthrough a firewall of the first cluster, the firewall configured toallow inbound communication based on an IP address of a search head ofthe second cluster that requests the information.
 11. The method asdescribed in claim 1 further comprising receiving, at the first cluster,the request for the information identifying the plurality of indexers ofthe first cluster through a firewall of the first cluster, the firewallconfigured to allow inbound communication based on an IP address of thesecond cluster that requests the information.
 12. The method asdescribed in claim 1, wherein the information includes a generationidentifier to be used in distributing the distributed search query, thegeneration identifier identifying an indexer as a primary indexer toperform the evaluation on data and return corresponding search resultswhen multiple indexers respectively manage a corresponding copy of thedata.
 13. The method as described in claim 1, wherein the informationincludes a generation identifier to be used in distributing thedistributed search query, the generation identifier identifying primaryand secondary indexers of the first cluster.
 14. The method as describedin claim 1, wherein the response includes event results associated withthe distributed search query.
 15. A non-transitory computer readablestorage media, storing software instructions, which when executed by oneor more processors, cause the one or more processors to performoperations comprising: determining, at a first cluster, informationidentifying a plurality of indexers of the first cluster based on amaster node of the first cluster identifying active indexers within thefirst cluster; transmitting, from the first cluster to a second cluster,the information identifying the plurality of indexers, wherein theinformation identifying the plurality of indexers comprises: a list ofactive indexers, and an indication of how to communicate with theplurality of indexers that is used by the second cluster in distributinga distributed search query to the plurality of indexers, the indicationincluding Internet Protocol addresses associated with the plurality ofindexers; receiving, at the plurality of indexers of the first cluster,the distributed search query from the second cluster, wherein thedistributed search query is distributed across the plurality of indexersbased on the information identifying the plurality of indexers; andproviding, at the first cluster, a response to the distributed searchquery from at least one of the plurality of indexers, wherein eachresponse from a respective indexer is generated by the respectiveindexer based on an evaluation, by the respective indexer, of thedistributed search query.
 16. The non-transitory computer readablestorage media of claim 15 further comprising receiving a request for theinformation identifying the plurality of indexers of the first clusterthrough a firewall of the first cluster.
 17. The non-transitory computerreadable storage media of claim 15, wherein the transmitting of theinformation identifying the plurality of indexers is through a firewallof the second cluster.
 18. A computer-implemented system, comprising:one or more processors; one or more computer readable storage media;determining, at a first cluster, information identifying a plurality ofindexers of the first cluster based on a master node of the firstcluster identifying active indexers within the first cluster;transmitting, from the first cluster to a second cluster, theinformation identifying the plurality of indexers, wherein theinformation identifying the plurality of indexers comprises: a list ofactive indexers, and an indication of how to communicate with theplurality of indexers that is used by the second cluster in distributinga distributed search query to the plurality of indexers, the indicationincluding Internet Protocol addresses associated with the plurality ofindexers; receiving, at the plurality of indexers of the first cluster,the distributed search query from the second cluster, wherein thedistributed search query is distributed across the plurality of indexersbased on the information identifying the plurality of indexers; andproviding, at the first cluster, a response to the distributed searchquery from at least one of the plurality of indexers, wherein eachresponse from a respective indexer is generated by the respectiveindexer based on an evaluation, by the respective indexer, of thedistributed search query.
 19. The system of claim 18, wherein the firstcluster is a cloud-based cluster and the second cluster is anon-premises cluster.